Add actions for docs build

.github/workflows/docs_pr.yml

@@ -0,0 +1,20 @@
+name: "Pull Request Docs Check"
+
+on: [pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - uses: ammaraskar/sphinx-action@master
+      with:
+        docs-folder: "docs/"
+
+    - uses: actions/upload-artifact@v1
+      with:
+        name: DocumentationHTML
+        path: docs/_build/html/

.github/workflows/docs_push.yml

@@ -0,0 +1,44 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - uses: ammaraskar/sphinx-action@master
+      with:
+        docs-folder: "docs/"
+
+    - uses: actions/upload-artifact@v1
+      with:
+        name: DocumentationHTML
+        path: docs/_build/html/
+
+    # Publish built docs to gh-pages branch.
+    # ===============================
+    - name: Commit documentation changes
+      run: |
+        git clone https://github.com/bacpop/PopPUNK.git --branch gh-pages --single-branch gh-pages
+        cp -r docs/_build/html/* gh-pages/
+        cd gh-pages
+        git config --local user.email "[email protected]"
+        git config --local user.name "GitHub Action"
+        git add .
+        git commit -m "Update documentation" -a || true
+        # The above command will fail if no changes were present, so we ignore
+        # the return code.
+    - name: Push changes
+      uses: ad-m/github-push-action@master
+      with:
+        branch: gh-pages
+        directory: gh-pages
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+    # ===============================