ci: workflow to generate feature matrix

.github/workflows/feature_matrix.yml

@@ -0,0 +1,37 @@
+name: Sync Feature Matrix
+
+on:
+  workflow_dispatch:
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Download and parse sheet
+        env:
+          SHEET_ID: ${{ secrets.FEATURE_MATRIX_SHEET_ID }}
+        run: curl -s https://docs.google.com/spreadsheets/d/$SHEET_ID/gviz/tq?tqx=out:html | pandoc --from html --to markdown_strict+pipe_tables -o doc/src/feature-matrix.md
+      - name: Clean up the document
+        run: |
+          # add title
+          sed -i "1i# Feature Matrix\nComparison of implemented features across Revolt's clients.\n" doc/src/feature-matrix.md
+
+          # replace the indicators
+          sed -i 's/| O /| ✅ /g' doc/src/feature-matrix.md
+          sed -i 's/| X /| ❌ /g' doc/src/feature-matrix.md
+          sed -i 's/| Partly /| 🚧 /g' doc/src/feature-matrix.md
+          sed -i 's/| NoPlan /| ⛔ /g' doc/src/feature-matrix.md
+
+          # remove extra rows
+          sed -i '4d' doc/src/feature-matrix.md
+          sed -i '4d' doc/src/feature-matrix.md
+          sed -i '4d' doc/src/feature-matrix.md
+
+          # set column properties again (while adding header line)
+          sed -i '5i |---|---|---|---|:-:|:-:|:-:|:-:|:-:|' doc/src/feature-matrix.md
+      - name: Commit changes
+        run: |
+          git config --global user.name 'Revolt CI'
+          git config --global user.email '[email protected]'
+          git commit -am "chore(docs): update feature matrix"
+          git push