Added github action to test on each push

On each push the mvn test will run on Ubuntu 18.04, latest OSX and latest Windows using JDK 8, 11 and 15

.github/workflows/ci.yml

@@ -0,0 +1,26 @@
+---
+name: Java CI
+
+on: [push]
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, macOS-latest, windows-latest]
+        java: [8, 11, 15]
+      fail-fast: false
+      max-parallel: 4
+    name: Test JDK ${{ matrix.java }}, ${{ matrix.os }}
+
+    steps:
+      - uses: actions/checkout@v1
+      - name: Set up JDK
+        uses: actions/setup-java@v1
+        with:
+          java-version: ${{ matrix.java }}
+      - name: Test with Maven
+        run: mvn test -B --file pom.xml
+
+...