docs: add github actions documentation

docs/deployment/continuous-integration/github-actions.md

@@ -0,0 +1,31 @@
+# Github Actions
+
+The Dokku project has an official Githb Action available on the [Github Marketplace](https://github.com/marketplace/actions/dokku). The simplest usage example is as follows:
+
+```yaml
+---
+name: 'deploy'
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Cloning repo
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Push to dokku
+        uses: dokku/github-action@v1
+        with:
+          git_remote_url: 'ssh://dokku@dokku.me:22/appname'
+          ssh_private_key: ${{ secrets.SSH_PRIVATE_KEY }}
+```
+
+
+For further usage documentation and other advanced examples, see the entry on the [Github Marketplace](https://github.com/marketplace/actions/dokku).