Init github action

.github/workflows/build.yml

+# This workflow will build a Java project with Maven
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
+
+name: build
+
+on:
+  push:
+    branches: [ master ]
+    paths-ignore: [ '**/*.md' ]
+  pull_request:
+    branches: [ master ]
+    paths-ignore: [ '**/*.md' ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        jdk: [7, 11]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK
+      uses: actions/setup-java@v1
+      with:
+        java-version: ${{ matrix.jdk }}
+    - name: Cache Maven packages
+      uses: actions/cache@v1
+      with:
+        path: ~/.m2
+        key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
+        restore-keys: ${{ runner.os }}-m2
+    - name: Build SDK with JDK 7
+      if: matrix.jdk == '7'
+      run: mvn clean compile -pl apollo-client,apollo-mockserver,apollo-openapi -am
+    - name: Full Build
+      if: matrix.jdk != '7'
+      run: mvn clean compile