Action to update dev docs (https://github.com/enso-org/ide/pull/618)

Original commit: d4db47ca02

gui/.github/workflows/docs.yml

@@ -0,0 +1,39 @@
+name: Publish Developer Docs
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'docs/**'
+
+jobs:
+  checkout:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        repository: 'enso-org/enso-org.github.io'
+        ref: 'sources'
+        token: ${{ secrets.ENSO_PAT }}
+    - name: set identity email
+      run: git config --global user.email "actions@github.com"
+    - name: set identity name
+      run: git config --global user.name "GitHub Actions"
+    - name: Checkout submodules
+      run: git submodule update --init
+    - name: Update submodules
+      id: status
+      run: |
+        git submodule update --init
+        git submodule update --remote --merge
+        if [ -n "$(git status --porcelain)" ]; then
+          echo "::set-output name=has_changes::1"
+        fi
+    - name: Push changes
+      run: |
+        git add .
+        git commit -m "Update submodules"
+        git push origin sources
+      if: steps.status.outputs.has_changes == '1'
+