Add Continous Integration

Github service to check if any commit to master or pull request to master is able to build. To be used in pull requests to make sure code will build before a code review.

.github/workflows/gradle.yml

@@ -0,0 +1,23 @@
+name: Java CI
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: Set up JDK 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.12
+    - name: Change wrapper permissions
+      run: chmod +x ./gradlew
+    - name: Build with Gradle
+      run: ./gradlew build