Add Github Actions (prebid#563)

DGarbar · rpanchyk · commit 8d778c581fd1 · 2019-12-13T16:16:21.000+02:00
Add some badges to README.md.
I decided to not include build on `push` to master. Bc we always use PRs for all features. Also, you can include 11 to `strategy.matrix.java` to verify version compatibility.
Be aware, that Java CI will be triggered by all `pull_request` event types (after each commit)

Later I want to add separate workflow to build Docker image on `release` event.
diff --git a/.github/workflows/pullrequest.yml b/.github/workflows/pullrequest.yml
@@ -0,0 +1,39 @@
+name: Java CI
+
+on:
+  pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '.github/**'
+    branches:
+      - master
+  release:
+    types:
+      - created
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        java: [8]
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - name: Set up JDK
+      uses: actions/setup-java@v1
+      with:
+        java-version: ${{ matrix.java }}
+
+    - name: Cache Maven dependendcies
+      uses: actions/cache@v1
+      with:
+        path: ~/.m2/repository
+        key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+        restore-keys: |
+          ${{ runner.os }}-maven-
+
+    - name: Build with Maven
+      run: mvn -B package --file pom.xml
diff --git a/README.md b/README.md
@@ -1,6 +1,12 @@
 ## This code is being used in production by multiple Prebid.org members, but is not the "official" version. See https://github.com/prebid/prebid-server/
 
 # Prebid Server
+[![GitHub version](https://badge.fury.io/gh/rubicon-project%2fprebid-server-java.svg)](http://badge.fury.io/gh/rubicon-project%2fprebid-server-java)
+[![Language grade: Java](https://img.shields.io/lgtm/grade/java/g/rubicon-project/prebid-server-java.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/rubicon-project/prebid-server-java/context:java)
+[![Total alerts](https://img.shields.io/lgtm/alerts/g/rubicon-project/prebid-server-java.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/rubicon-project/prebid-server-java/alerts/)
+[![GitHub contributors](https://img.shields.io/github/contributors/rubicon-project/prebid-server-java.svg)](https://GitHub.com/rubicon-project/prebid-server-java/contributors/)
+[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](https://github.com/rubicon-project/prebid-server-java/blob/master/docs/contributing.md) 
+[![GitHub pull-requests closed](https://img.shields.io/github/issues-pr-closed/rubicon-project/prebid-server-java.svg)](https://GitHub.com/rubicon-project/prebid-server-java/pull/)
 
 Prebid Server is an open source implementation of Server-Side Header Bidding.
 It is managed by [Prebid.org](http://prebid.org/overview/what-is-prebid-org.html),
