chore(actions): test docs in every PR (#7)

.github/workflows/docs.yaml

@@ -7,6 +7,7 @@ on:
     paths:
     - docs/**
     - mkdocs.yml
+    - pyproject.toml
     branches:
     - main
   release:

.github/workflows/pull-request.yaml

@@ -47,3 +47,31 @@ jobs:
     - name: Coverage Tests
       run: |
         make test-cov
+
+  validate-docs:
+    name: Validate Docs
+    runs-on: ubuntu-22.04
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Setup Python
+      uses: actions/setup-python@v4
+      with:
+        python-version: "3.10"
+
+    - name: Cache pip dependencies
+      id: cache
+      uses: actions/cache@v3
+      with:
+        path: ~/.cache/pip
+        key: ${{ runner.os }}-pip-${{ hashFiles('pyproject.toml') }}
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        make install-doc
+
+    - name: Build docs
+      run: |
+        mkdocs build