Add codespell to CI

Author: DimitriPapadopoulos

.github/workflows/codespell.yml

@@ -0,0 +1,20 @@
+---
+name: Codespell
+
+on:
+  push:
+
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  codespell:
+    name: Check for spelling errors
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: codespell-project/actions-codespell@master
+        with:
+          skip: js,*.svg