Switch to GH-Workflow & use java 16 on jitpack builds (#1236)

* Add github actions workflow
* Add jitpack.yml to configure java version

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: ProtocolLib full build lifecycle
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup java
+        uses: actions/setup-java@v2
+        with:
+          distribution: 'adopt'
+          java-version: '16'
+          check-latest: true
+
+      - name: Run maven build lifecycle
+        run: mvn --batch-mode clean test package
+
+      - name: Upload plugin file
+        uses: actions/upload-artifact@v2
+        with:
+            name: ProtocolLib
+            path: target/ProtocolLib.jar

jitpack.yml

@@ -0,0 +1,2 @@
+before_install:
+  - sdk install java 16.0.1-adpt