ci: add GitHub Actions for PR type-check and npm publish on tags

.github/workflows/ci.yml

@@ -0,0 +1,20 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  typecheck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+          cache-dependency-path: gitnexus/package-lock.json
+      - run: npm ci
+        working-directory: gitnexus
+      - run: npx tsc --noEmit
+        working-directory: gitnexus

.github/workflows/publish.yml

@@ -0,0 +1,28 @@
+name: Publish to npm
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          registry-url: https://registry.npmjs.org
+          cache: npm
+          cache-dependency-path: gitnexus/package-lock.json
+      - run: npm ci
+        working-directory: gitnexus
+      - run: npx tsc --noEmit
+        working-directory: gitnexus
+      - run: npm publish
+        working-directory: gitnexus
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}