add workflow to validate against .md file changes

.github/workflows/check-documentation.yml

@@ -0,0 +1,77 @@
+name: ocelot.social check documentation
+
+on:
+  push:
+    branches:
+      - trigger-docs.ocelot.social-deployment-by-markdown-file-changes-in-master-branch
+
+jobs:
+  files-changed:
+    name: Detect File Changes - Markdown files
+    runs-on: ubuntu-latest
+    outputs:
+      markdown-files: ${{ steps.changes.outputs.markdown-files }}
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@master
+
+      - name: Check for markdown file changes
+        uses: dorny/paths-filter@v2.11.1
+        id: changes
+        with:
+          token: ${{ github.token }}
+          filters: .github/file-filters.yml
+          list-files: shell
+
+  check-summary:
+    name: Check documentation summary
+    if: needs.files-changed.outputs.markdown-files == 'true'
+    needs: files-changed
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@master
+
+      - name: Check, if all .md files listed in SUMMARY.dm exist in current branch
+        run: |
+          if [ ! -f "SUMMARY.md" ]; then
+            echo "The file SUMMARY.md does not exist."
+            exit 1
+          fi
+
+          md_files=$(grep -o -P '\[[^\]]+\]\(([^)]+\.md)\)' SUMMARY.md | sed -r 's/.*\(([^)]+)\)/\1/')
+          missing_files=()
+
+          for file in $md_files; do
+            if [ ! -f "$file" ]; then
+              missing_files+=("$file")
+            fi
+          done
+
+          if [ ${#missing_files[@]} -eq 0 ]; then
+            echo "All .md files listed in SUMMARY.dm exist."
+          else
+            echo "These files listed in SUMMARY.dm do not exist:"
+            for missing_file in "${missing_files[@]}"; do
+              echo "$missing_file"
+            done
+            exit 1
+          fi
+
+  check-markdown-links:
+    name: Check Markdown links
+    if: needs.files-changed.outputs.markdown-files == 'true'
+    needs: files-changed
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@master
+    - name: Check Markdown Links
+      uses: gaurav-nelson/github-action-markdown-link-check@master
+      with:
+        use-quiet-mode: 'yes'
+        use-verbose-mode: 'no'
+        check-modified-files-only: 'no'
+        config-file: '.github/workflows/mlc_config.json'
+        base-branch: 'trigger-docs.ocelot.social-deployment-by-markdown-file-changes-in-master-branch' # set to branch of current PR's branch
+        folder-path: '.'