add build workflow

.gitea/workflows/build.yml

@@ -0,0 +1,21 @@
+name: Gitea Actions Demo
+run-name: ${{ gitea.actor }} is testing out Gitea Actions 🚀
+on: [push, workflow_dispatch]
+
+jobs:
+  Explore-Gitea-Actions:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-java@v5
+        with:
+          distribution: 'temurin'
+          java-version: '25'
+      - run: ./gradlew assemble
+      - run: ./gradlew test
+      - run: ./gradlew jar
+      - uses: actions/upload-artifact@v4
+        with:
+          name: "griefalert-${{ gitea.sha }}.jar"
+          path: build/libs/GriefAlert-*.jar
+          retention-days: 7