Replace release script with GitHub Actions workflow (#268)

Automating releases will make the process smoother, and less
open to mistakes

Author: Adrian Clay

.github/workflows/release.yml

@@ -0,0 +1,18 @@
+on:
+  push:
+    tags: "*"
+
+jobs:
+  push_to_dockerhub:
+    name: "Push Docker Images to DockerHub"
+    strategy:
+      matrix:
+        image:
+          - {folder: service, dockerhub_name: nia-111-adaptor}
+          - {folder: nginx, dockerhub_name: nia-111-nginx-adaptor}
+    uses: NHSDigital/integration-adaptor-actions/.github/workflows/release-adaptor-container-image.yml@main
+    with:
+      dockerhub_name: ${{matrix.image.dockerhub_name}}
+      folder: ${{matrix.image.folder}}
+
+    secrets: inherit