feat: add GitHub Actions CI/CD workflows

- Add continuous testing workflow for Node.js 16, 18, and 20
- Add cross-platform testing for Ubuntu, Windows, and macOS
- Run tests on push to main/master branches and on PRs
- Include build verification in CI pipeline

Author: EvanBacon

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    
+    strategy:
+      matrix:
+        node-version: [16.x, 18.x, 20.x]
+    
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+    
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'yarn'
+    
+    - name: Install dependencies
+      run: yarn install --frozen-lockfile
+    
+    - name: Run tests
+      run: yarn test
+    
+    - name: Build project
+      run: yarn build
+
+  lint-and-format:
+    runs-on: ubuntu-latest
+    
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+    
+    - name: Use Node.js 18.x
+      uses: actions/setup-node@v4
+      with:
+        node-version: 18.x
+        cache: 'yarn'
+    
+    - name: Install dependencies
+      run: yarn install --frozen-lockfile
+    
+    - name: Check TypeScript types
+      run: yarn build

.github/workflows/cross-platform.yml

@@ -0,0 +1,35 @@
+name: Cross-Platform Tests
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  test-cross-platform:
+    runs-on: ${{ matrix.os }}
+    
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        node-version: [18.x]
+    
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+    
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'yarn'
+    
+    - name: Install dependencies
+      run: yarn install --frozen-lockfile
+    
+    - name: Run tests
+      run: yarn test
+    
+    - name: Build project
+      run: yarn build