Add workflow to generate docs

.github/workflows/generate_docs.yml

@@ -0,0 +1,22 @@
+name: docs
+on: [push, pull_request]
+
+
+jobs:
+  build-docs:
+    name: Build and generate docs
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Set up Python 3.8
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+    - name: Build docs
+      run: |
+        - pip install --upgrade -r requirements_docs.txt
+        - pip install --upgrade .[all]
+        - mkdir docs_build
+        - sphinx-build -nW -b html docs docs_build