Github action in pull request

Author: hannesa2

.github/workflows/build.yml

@@ -3,8 +3,8 @@ name: Build
 on:
   push:
     branches:
-      - 'master'
-      - 'develop'
+      - master
+  pull_request:
 
 jobs:
   build:
@@ -13,8 +13,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - name: set up JDK 11
-        uses: actions/setup-java@v1
+      - uses: actions/setup-java@v1
         with:
           java-version: 11
       - name: Make gradlew executable