docs: build and deploy to github pages

Signed-off-by: Jérémie Drouet <jeremie.drouet@gmail.com>

.github/workflows/doc.yml

@@ -0,0 +1,18 @@
+name: building github pages documentation
+
+on:
+  push:
+    branches:
+      - stable
+
+jobs:
+  build-and-deploy:
+    name: building documentation and deploying it on gh-pages branch
+    runs-on: ubuntu-latest
+    steps:
+      - name: pull the code
+        uses: actions/checkout@v2
+      - name: install dependencies
+        run: pip install -r requirements.txt
+      - name: build and deploy
+        run: mkdocs gh-deploy -f docs/en/mkdocs.yml