ci: add GitHub Actions workflow for testing build

...and performing security scan.

ING-4068

.github/workflows/build.yml

@@ -0,0 +1,20 @@
+name: Build
+
+on:
+  pull_request:
+    branches:
+      - master
+
+  # Note: Images are currently published via Docker Hub automated build
+
+  push:
+    branches:
+      - master
+  workflow_dispatch: {}
+
+jobs:
+  build:
+    uses: wetransform/gha-workflows/.github/workflows/dockerfile-build.yml@master
+    with:
+      image: wetransform/conversion-gdal
+      tag: ci