Add CI workflow for tests (#2)

* Add initial test workflow

* Move test workflow to new directory

* Use xvfb for graphic tests

Author: eomielan

.github/workflows/tests.yml

@@ -0,0 +1,38 @@
+name: Build and Test
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Node.js
+      uses: actions/setup-node@v2
+      with:
+        node-version: '20'
+
+    - name: Install dependencies
+      run: yarn install
+
+    - name: Set up Xvfb
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y xvfb
+        Xvfb :99 -screen 0 1920x1080x24 &
+        echo "DISPLAY=:99" >> $GITHUB_ENV
+
+    - name: Run ESLint
+      run: yarn eslint src
+
+    - name: Run tests
+      run: yarn test