Use docs/requirements.txt for documentation build dependencies in CI

Author: lavr

.github/workflows/tests.yaml

@@ -61,6 +61,22 @@ jobs:
       - name: run django tests
         run: tox -e ${{ matrix.tox }}
 
+  docs:
+    name: "docs"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+          cache: pip
+      - name: install dependencies
+        run: |
+          pip install -e .
+          pip install sphinx -r docs/requirements.txt
+      - name: build docs
+        run: sphinx-build -W -b html docs docs/_build/html
+
   typecheck:
     name: "typecheck"
     runs-on: ubuntu-latest