docs: spelling & grammar fixes & GitHub Action (#3490)

.github/workflows/docs.yml

@@ -0,0 +1,24 @@
+name: Documentation
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - '**/*.md'
+  pull_request:
+    paths:
+      - '**/*.md'
+
+jobs:
+  spelling:
+    name: 'Spelling & Grammar'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Install Dependencies
+        run: |
+          sudo npm install --global spellchecker-cli
+      - name: Spell check
+        run: |
+          spellchecker --quiet --files="**/*.md" --dictionaries="./.spellcheck.dict.txt" --reports="spelling.json" --plugins spell indefinite-article repeated-words syntax-mentions syntax-urls frontmatter