Publish to npm for new sdk versions

If the API or the sdk templates increment their version we want to
publish a copy of the package to npm.

The GitHub action we are using here (npm-publish) claims that it will
only publish if the package version has changed from the published
version.

Issue #497 Integrate SDK generation into build process

.github/workflows/sdk.yml

@@ -22,12 +22,17 @@ jobs:
           path: 'sdk'
       - name: Copy API definition
         run: cp service/src/openapi.json sdk/openapi.json
-      - name: Invoke the typescript generator
+      - name: Invoke the TypeScript generator
         working-directory: sdk
         run: ./gradlew generateSwaggerCode
-      - name: Install dependencies for the typescript sdk
+      - name: Install dependencies for the TypeScript SDK
         working-directory: sdk/build/typescript
         run: npm ci
-      - name: Build the typescript sdk
+      - name: Build the TypeScript SDK
         working-directory: sdk/build/typescript
         run: npm run build
+      - name: Publish to NPM if there is a new version
+        uses: JS-DevTools/npm-publish@v3
+        with:
+          package: sdk/build/typescript
+          token: ${{ secrets.NPM_TOKEN }}