Run tests for master branch and pull requests

.github/workflows/tests.yml

@@ -0,0 +1,25 @@
+name: Build and test Minestom
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 11
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.11
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Build Minestom
+      run: ./gradlew build
+    - name: Run tests
+      run: ./gradlew test