ci(npm): publish to npm on tag creation (#1997)

* Create npm.yml

* fix invalid on

* Update dnt.ts

* Update npm.yml

.github/workflows/npm.yml

@@ -0,0 +1,33 @@
+name: NPM Publish
+
+on:
+  create:
+    tags:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        deno: ["v1.x"]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: denoland/setup-deno@main
+        with:
+          deno-version: ${{ matrix.deno }}
+      # Taken from: https://github.com/denoland/dnt#github-actions---npm-publish-on-tag
+      - name: Get tag version
+        if: startsWith(github.ref, 'refs/tags/')
+        id: get_tag_version
+        run: echo ::set-output name=TAG_VERSION::${GITHUB_REF/refs\/tags\//}
+      - uses: actions/setup-node@v2
+        with:
+          node-version: '16.x'
+          registry-url: 'https://registry.npmjs.org'
+      - name: npm build
+        run: deno run -A ./dnt.ts ${{steps.get_tag_version.outputs.TAG_VERSION}}
+      - name: npm publish
+        if: startsWith(github.ref, 'refs/tags/')
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+        run: cd npm && npm publish