ci: add npm publish workflow and clean up package.json

- Add .github/workflows/publish.yml
- Remove .npmrc and unused sharp config
- Package ready for auto-publishing

.github/workflows/publish.yml

@@ -0,0 +1,32 @@
+name: Publish to npm
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "src/**"
+      - "package.json"
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Install dependencies
+        run: bun install
+
+      - name: Build
+        run: bun run build
+
+      - name: Setup npm auth
+        run: echo "//registry.npmjs.org/:_authToken=${{ secrets.NPM_TOKEN }}" > ~/.npmrc
+
+      - name: Publish
+        run: npm publish --access public
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}