Add release workflow

.github/workflows/main.yml

@@ -0,0 +1,29 @@
+name: build
+# Controls when the action will run. 
+on:
+  push:
+    branches: [ main ]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: checkout
+      uses: actions/checkout@v1
+    - name: setup
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - name: cache
+      uses: actions/cache@v1
+      with:
+        path: ~/.m2/repository
+        key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+        restore-keys: |
+          ${{ runner.os }}-maven-
+    - name: build
+      run: mvn install
+    - name: artifact
+      uses: actions/upload-artifact@v1
+      with:
+        name: Bolty.jar
+        path: target/PGM.jar