Create GH Actions CI pipeline (#3)

The workflow builds the Docker image.

Author: mrsarm

.github/workflows/docker-image.yml

@@ -0,0 +1,14 @@
+name: Docker Image CI
+
+on: [push, pull_request]
+
+jobs:
+
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build the Docker image
+      run: ./docker-build.sh