Add gen-docs job to github workflows (#5)

Author: stefan-brus-frequenz

.github/workflows/ci.yaml

@@ -31,6 +31,27 @@ jobs:
       - name: Run protolint
         run: protolint lint proto
 
+  gen-docs:
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Fetch sources
+        uses: actions/checkout@v3
+        with:
+          submodules: true
+
+      - name: Generate documentation
+        run: |
+          docker run --rm -v $PWD:$PWD pseudomuto/protoc-gen-doc \
+            -I $PWD/proto \
+            -I $PWD/submodules/api-common-protos \
+            -I $PWD/submodules/frequenz-api-common/proto \
+            --doc_opt=markdown,gen-docs.md --doc_out=$PWD \
+            $(find $PWD/proto -name *.proto)
+
+      - name: Write summary
+        run: cat gen-docs.md > $GITHUB_STEP_SUMMARY
+
   tests:
     needs: ["protolint"]
     strategy: