build(cspell): add cspell github-action

.github/workflows/cspell.yml

@@ -0,0 +1,51 @@
+name: 'Check spelling'
+on: # rebuild any PRs and main branch changes
+  pull_request:
+  push:
+
+jobs:
+  spellcheck: # run the action
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: streetsidesoftware/cspell-action@v1.0.1
+        with:
+          # Github token used to fetch the list of changed files in the commit.
+          # Default: ${{ github.token }}
+          github_token: ${{ secrets.github_token }}
+
+          # Define glob patterns to filter the files to be checked. Use a new line between patterns to define multiple patterns.
+          # The default is to check ALL files that were changed in in the pull_request or push.
+          # Note: `ignorePaths` defined in cspell.json still apply.
+          # Example:
+          # files: |
+          #   **/*.{ts,js}
+          #   !dist/**/*.{ts,js}
+          #   # Hidden directories need an explicit .* to be included
+          #   .*/**/*.yml
+          #
+          # To not check hidden files, use:
+          # files: "**"
+          #
+          # Default: ALL files
+          files: ''
+
+          # The point in the directory tree to start spell checking.
+          # Default: .
+          root: '.'
+
+          # Notification level to use with inline reporting of spelling errors.
+          # Allowed values are: warning, error, none
+          # Default: warning
+          inline: warning
+
+          # Determines if the action should be failed if any spelling issues are found.
+          # Allowed values are: true, false
+          # Default: true
+          strict: true
+
+          # Limit the files checked to the ones in the pull request or push.
+          # incremental_files_only: false
+
+          # Path to `cspell.json`
+          config: '.'