Refactor Gradle CI workflow for Java 21 support

Updated the Gradle workflow to use Java 21 and streamlined the build process.

Author: chughes102212-stack

.github/workflows/gradle.yml

@@ -0,0 +1,28 @@
+name: Build Mod Without Local JDK
+
+on: [push, workflow_dispatch]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+
+      - name: Set up Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: '21' # Change to 17 or 8 depending on the Minecraft version
+
+      - name: Make Gradle Executable
+        run: chmod +x gradlew
+
+      - name: Build with Gradle
+        run: ./gradlew build
+
+      - name: Upload Mod Jar
+        uses: actions/upload-artifact@v4
+        with:
+          name: compiled-mod
+          path: build/libs/*.jar