fix(cdn): change default value of baseUrl to empty string (#423)

`cdnBaseUrl` is settable via the project.json or via attribute/property. The property takes precedence over the project.json, and if neither is defined it defaults to unpkg.com. By having a default value for the property, then in order to take a value from the config, then the user would need to explicitly set the property / attribute to `''`.

Confirmed this works by setting the cdnBaseUrl in project/project.json in the configurator

Author: e111077

README.md

@@ -682,7 +682,7 @@ All-in-one project, editor, file switcher, and preview with a horizontal side-by
 | -------------------- | -------------------------------- | ------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `projectSrc`         | `string`                         | `undefined`               | URL of the [project manifest](#project-manifest) to load                                                                                                                                           |
 | `config`             | `ProjectManifest`                | `undefined`               | Get or set the project configuration and files, ([details](#option-3-config-property)).                                                                                                            |
-| `cdnBaseUrl`         | `string`                         | `https://unpkg.com`       | Change the underlying npm CDN base url. Confirmed tested are `htts://unpkg.com` and `https://cdn.jsdelivr.net/npm`                                                                                 |
+| `cdnBaseUrl`         | `string`                         | `""`                      | Change the underlying npm CDN base url. Confirmed tested are `htts://unpkg.com` and `https://cdn.jsdelivr.net/npm`. Note: Default `""` resolves to `https://unpkg.com`                             |
 | `lineNumbers`        | `boolean`                        | `false`                   | Render a gutter with line numbers in the editor                                                                                                                                                    |
 | `lineWrapping`       | `boolean`                        | `false`                   | If `true`, long lines are wrapped, otherwise the editor will scroll.                                                                                                                               |
 | `editableFileSystem` | `boolean`                        | `false`                   | Allow adding, removing, and renaming files                                                                                                                                                         |
@@ -713,7 +713,7 @@ project element.
 | ---------------- | ----------------------------- | ------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `projectSrc`     | `string`                      | `undefined`               | URL of a [project files manifest](#option-2-json-manifest) to load.                                                                                                                                |
 | `config`         | `ProjectManifest`             | `undefined`               | Get or set the project configuration and files, ([details](#option-3-config-property)).                                                                                                            |
-| `cdnBaseUrl`     | `string`                      | `https://unpkg.com`       | Change the underlying npm CDN base url. Confirmed tested are `htts://unpkg.com` and `https://cdn.jsdelivr.net/npm`                                                                                 |
+| `cdnBaseUrl`     | `string`                      | `""`                      | Change the underlying npm CDN base url. Confirmed tested are `htts://unpkg.com` and `https://cdn.jsdelivr.net/npm`. Note: Default `""` resolves to `https://unpkg.com`                             |
 | `sandboxScope`   | `string`                      | `"playground-elements"`   | The service worker scope to register on.                                                                                                                                                           |
 | `sandboxBaseUrl` | `string`                      | _module parent directory_ | Base URL for untrusted JavaScript execution (⚠️ use with caution, see [sandbox security](#sandbox-security)). Resolved relative to the module containing the definition of `<playground-project>`. |
 | `diagnostics`    | `Map<string, lsp.Diagnostic>` | `undefined`               | Map from filename to array of Language Server Protocol diagnostics resulting from the latest compilation.                                                                                          |

src/configurator/knobs.ts

@@ -136,7 +136,8 @@ export const knobs = [
     id: 'cdnBaseUrl',
     label: 'CDN Base URL',
     section: 'features',
-    default: 'https://unpkg.com',
+    default: '',
+    placeholder: 'Resolves to https://unpkg.com',
     htmlAttribute: 'cdn-base-url',
     inputType: 'text',
   }),

src/playground-ide.ts

@@ -221,11 +221,12 @@ export class PlaygroundIde extends LitElement {
    * Base URL for the CDN used to resolve bare module specifiers.
    *
    * Examples:
-   * - "https://unpkg.com" (default)
+   * - "" (default, but resolves to "https://unpkg.com")
+   * - "https://unpkg.com"
    * - "https://cdn.jsdelivr.net/npm"
    */
   @property({attribute: 'cdn-base-url'})
-  cdnBaseUrl = 'https://unpkg.com';
+  cdnBaseUrl = '';
 
   /**
    * Allow the user to add, remove, and rename files in the project's virtual

src/playground-project.ts

@@ -178,11 +178,12 @@ export class PlaygroundProject extends LitElement {
    * Base URL for the CDN used to resolve bare module specifiers.
    *
    * Examples:
+   * - "" (default, but resolves to "https://unpkg.com")
    * - "https://unpkg.com" (default)
    * - "https://cdn.jsdelivr.net/npm"
    */
   @property({attribute: 'cdn-base-url'})
-  cdnBaseUrl = 'https://unpkg.com';
+  cdnBaseUrl = '';
 
   /**
    * The service worker scope to register on