Update docs workflow. (#143)

.github/workflows/build_docs.yml

@@ -10,32 +10,22 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Python
-        uses: actions/setup-python@v3
+        uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: '3.12'
+          cache: pip
+          cache-dependency-path: requirements.txt
 
       - name: Upgrade pip
         run: |
           # install pip=>20.1 to use "pip cache dir"
-          python3 -m pip install --upgrade pip
-
-      - name: Get pip cache dir
-        id: pip-cache
-        run: echo "::set-output name=dir::$(pip cache dir)"
-
-      - name: Cache dependencies
-        uses: actions/cache@v2
-        with:
-          path: ${{ steps.pip-cache.outputs.dir }}
-          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
-          restore-keys: |
-            ${{ runner.os }}-pip-
+          python -m pip install --upgrade pip
 
       - name: Install dependencies
-        run: python3 -m pip install -r ./requirements.txt
+        run: python -m pip install -r ./requirements.txt
 
       - run: |
           cd docs

requirements.txt

@@ -18,4 +18,4 @@ pre-commit
 
 # docs
 sphinx
-sphinx-rtd-theme==0.5.1 #latest is 0.5.2 but requires docutils < 0.16, 1.0.0 is coming https://sphinx-rtd-theme.readthedocs.io/en/latest/changelog.html#v0-5-2
+sphinx-rtd-theme