⭕ re-add action workflow

Took 1 minute

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: Auction House Build
+
+on: [ push, pull_request ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v2
+
+      - name: Set up JDK 16
+        uses: actions/setup-java@v2
+        with:
+          distribution: 'temurin'
+          java-version: '8'
+
+      - name: Cache Maven Packages
+        uses: actions/cache@v2
+        with:
+          path: ~/.m2
+          key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
+          restore-keys: ${{ runner.os }}-m2
+
+      - name: Build with Maven
+        run: mvn verify -B --file pom.xml