(#43) Add the Publish Docker workflow.

Author: paveloom

.github/workflows/publish-docker.yml

@@ -0,0 +1,20 @@
+name: Publish Docker
+
+on:
+  push:
+    branches:
+      - docker
+
+jobs:
+  Update:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: Publish to Registry
+      uses: elgohr/Publish-Docker-Github-Action@master
+      with:
+        name: paveloom-c/GPKernels/c-gpkernels
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+        registry: docker.pkg.github.com
+        tags: "latest"