Set up a GHA npm publish job

.github/workflows/npm-publish.yml

@@ -0,0 +1,36 @@
+name: Npm directory update
+on:
+  workflow_dispatch:
+jobs:
+  publish:
+    name: Build, bump & publish to npm
+    runs-on: ubuntu-latest
+    container: httptoolkit/act-build-base:v3.0.0
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions/setup-node@v3
+        with:
+          node-version: '16.x'
+          registry-url: 'https://registry.npmjs.org'
+
+      - run: npm ci
+
+      # Check that the tests and overall build all still pass:
+      - run: npm test
+      - run: npm run build
+
+      # Create the new release:
+      - name: Bump version & push
+        run: |
+          git config --global user.name 'Automated publish'
+          git config --global user.email 'pimterry@users.noreply.github.com'
+
+          npm version patch
+
+          git push && git push --tags
+
+      # Publish the release to npm:
+      - run: npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_PUBLISH_TOKEN }}