add github workflows (#46)

.github/workflows/ci.yml

@@ -0,0 +1,35 @@
+name: Continuous Integration
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18.x]
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+
+    - name: Get Yarn cache directory
+      id: yarn-cache-dir-path
+      run: echo "dir=$(yarn cache dir)" >> $GITHUB_OUTPUT
+
+    - name: Use Yarn cache
+      uses: actions/cache@v4
+      id: yarn-cache
+      with:
+        path: ${{ steps.yarn-cache-dir-path.outputs.dir }}
+        key: ${{ runner.os }}-yarn-${{ matrix.node-version }}-${{ hashFiles('**/yarn.lock') }}
+
+    - name: Install dependencies
+      run: yarn install --prefer-offline --frozen-lockfile