Update github actions workflow

.github/workflows/build.yml

@@ -0,0 +1,50 @@
+name: "build"
+
+on: ["pull_request", "push"]
+ 
+jobs:
+  build:
+    strategy:
+      matrix:
+        java: ["1.8", "11"]
+        os: ["ubuntu-18.04"]
+    runs-on: "${{ matrix.os }}"
+    steps:
+    - name: "Checkout Repository"
+      uses: "actions/checkout@v2.3.4"
+    - name: "Setup JDK ${{ matrix.java }}"
+      uses: "actions/setup-java@v1.4.3"
+      with:
+          java-version: "${{ matrix.java }}"
+    - name: "Cache Gradle"
+      uses: "actions/cache@v2.1.3"
+      with:
+        path: |
+          "~/.gradle/caches"
+          "~/.gradle/wrapper"
+        key: "${{ runner.os }}-${{ matrix.java }}-gradle-${{ hashFiles('**/*.gradle*') }}"
+        restore-keys: |
+          "${{ runner.os }}-${{ matrix.java }}-gradle-"
+    - name: "Cache Local Maven Repository"
+      uses: "actions/cache@v2.1.3"
+      with:
+        path: "~/.m2/repository"
+        key: "${{ runner.os }}-${{ matrix.java }}-maven-${{ hashFiles('**/pom.xml') }}"
+        restore-keys: |
+          "${{ runner.os }}-${{ matrix.java }}-maven-"
+    - name: "Cache BuildTools Decompiled Code"
+      uses: "actions/cache@v2.1.3"
+      with:
+        path: "$GITHUB_WORKSPACE/work"
+        key: "${{ runner.os }}-buildtools"
+        restore-keys: |
+          "${{ runner.os }}-buildtools"
+    - name: "Test Enviornment"
+      run: "echo $GITHUB_WORKSPACE"
+    - name: "Download BuildTools"
+      run: "wget https://hub.spigotmc.org/jenkins/job/BuildTools/lastSuccessfulBuild/artifact/target/BuildTools.jar"
+    - name: "Run BuildTools"
+      run: "java -jar BuildTools.jar --rev 1.16.4"
+    - name: "Clean Build"
+      run: "./gradlew clean build sourcesJar javadocJar"
+