Add workflow for merge queue (#180)

Author: msimberg

.github/workflows/docs_merge_queue.yaml

@@ -0,0 +1,25 @@
+name: build docs (merge queue)
+
+on:
+  merge_group:
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: 3.x
+      - run: echo "cache_id=$(date --utc '+%V')" >> $GITHUB_ENV
+      - uses: actions/cache@v3
+        with:
+          key: mkdocs-material-${{ env.cache_id }}
+          path: .cache
+          restore-keys: |
+            mkdocs-material-
+      - run: pip install --upgrade pip
+      - run: |
+          pip install -r requirements.txt
+      - run: rm -rf site
+      - run: cat mkdocs.yml
+      - run: mkdocs build --strict