Update GitHub Actions to Gradle

.github/workflows/build.yml

@@ -12,12 +12,18 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3.3.0 #https://github.com/actions/checkout/releases
-    - name: Set up JDK 8
-      uses: actions/setup-java@v3.9.0 #https://github.com/actions/setup-java/releases
+    - uses: actions/checkout@v3
+    - name: Set up JDK 11
+      uses: actions/setup-java@v3
       with:
-        distribution: 'temurin'
-        java-version: 8
+        java-version: 11
+        distribution: 'adopt'
 
-    - name: Build with Maven
-      run: mvn -B package --file pom.xml
+    - name: Build with Gradle
+      run: gradlew build
+
+    - name: Upload Artifact
+      uses: actions/upload-artifact@v2
+      with:
+        name: Multiverse-Core-SNAPSHOT
+        path: build/libs/Multiverse-Core-4.3.2-SNAPSHOT.jar