chore: add GitHub action

Author: Niklas Kiefer

.github/workflows/CI.yml

@@ -0,0 +1,32 @@
+name: CI
+on: [ push, pull_request ]
+jobs:
+  Build:
+
+    strategy:
+      matrix:
+        os: [ ubuntu-latest ]
+        node-version: [ 14 ]
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Use Node.js
+      uses: actions/setup-node@v2
+      with:
+        node-version: ${{ matrix.node-version }}
+    - name: Cache Node.js modules
+      uses: actions/cache@v2
+      with:
+        # npm cache files are stored in `~/.npm` on Linux/macOS
+        path: ~/.npm
+        key: ${{ runner.OS }}-node-${{ hashFiles('**/package-lock.json') }}
+        restore-keys: |
+          ${{ runner.OS }}-node-
+          ${{ runner.OS }}-
+    - name: Install dependencies
+      run: npm install
+    - name: Build
+      run: npm run all

README.md

@@ -3,6 +3,8 @@
 
 # Custom Elements in bpmn-js
 
+[![CI](https://github.com/bpmn-io/bpmn-js-example-custom-elements/workflows/CI/badge.svg)](https://github.com/bpmn-io/bpmn-js-example-custom-elements/actions?query=workflow%3ACI)
+
 An example of how to support custom elements in [bpmn-js](https://github.com/bpmn-io/bpmn-js) while ensuring BPMN 2.0 compatibility.
 
 ![Screenshot](docs/screenshot.png)