Use concatenation to build the cdn url for the browser snippet

[matux]

Description of the change

Turns out, using concatenation results in a smaller minified file as the transpiler...

Turns this interpolated strings

export const defaultRollbarJsUrl = 'https://${cdnHost}/rollbarjs/refs/tags/v${version}/rollbar.min.js`;

into

var u="https://".concat("cdn.rollbar.com","/rollbarjs/refs/tags/v").concat("3.0.0-alpha.3","/rollbar.min.js");

While if we use concatenation, it turns

export const defaultRollbarJsUrl = 'https://' + cdnHost + '/rollbarjs/refs/tags/v' + version + '/rollbar.min.js';

into a static string:

"https://cdn.rollbar.com/rollbarjs/refs/tags/v3.0.0-alpha.3/rollbar.min.js"

This takes the size of rollbar.snippet.js back to its usual 6581 bytes.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release