Add github workflow to test that it compiles

.github/workflows/ant.yml

@@ -0,0 +1,22 @@
+name: Java CI
+
+on:
+  push:
+    branches: [ master, add-instructions ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 11
+      uses: actions/setup-java@v2
+      with:
+        java-version: '11'
+        distribution: 'temurin'
+    - name: Build with Ant
+      run: ant build