Add GitHub Actions build workflow for checking pull requests

.github/workflows/pr.yml

@@ -0,0 +1,35 @@
+# mirror of the Jenkins pipeline, used for requiring PRs to build successfully before merging
+# this uses Actions because it's easier to integrate with GitHub PRs, and to allow running the build on forks
+
+name: Build pull request
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: "17.0.1"
+      - uses: gradle/actions/setup-gradle@v3
+
+      - name: Clean
+        run: |
+          chmod +x gradlew
+          ./gradlew clean
+
+      - name: Build
+        run: ./gradlew build
+
+      - name: Run Datagen
+        run: ./gradlew runAllDatagen
+
+      - name: Check Datagen
+        run: |
+          git add --intent-to-add .
+          git diff --name-only --exit-code -- ":!:*/src/generated/resources/.cache/*"