[ci] Add spell check

.github/actions/spelling/allow.txt

@@ -0,0 +1 @@
+github

.github/workflows/spell_check.yml

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+name: Check Spelling
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
+jobs:
+  spelling:
+    name: Check Spelling
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'RT-Thread'
+    permissions:
+      contents: read
+      pull-requests: read
+      actions: read
+    steps:
+    - name: output ignore words info
+      run: |
+        echo "> If any words shown as incorrect are spelled correctly, please add them to .github/actions/spelling/allow.txt." >> $GITHUB_STEP_SUMMARY
+    - name: check spelling
+      id: spelling
+      uses: check-spelling/check-spelling@v0.0.20
+      with:
+        checkout: true
+        check_file_names: 0
+        only_check_changed_files: 1
+        post_comment: 0
+        extra_dictionaries:
+          cspell:en_US/src/en_US.txt
+          cspell:software-terms/softwareTerms.txt
+          cspell:python/python.txt
+          cspell:cpp/cpp.txt
+
+        check_extra_dictionaries: ''
+
+    - name: output Success info
+      run: |
+        echo "✅ Check spelling success." >> $GITHUB_STEP_SUMMARY