ci: configure npm auth and pass GITHUB_TOKEN for unstable publish (#14772)

Author: soberm

.github/workflows/release-unstable.yml

@@ -29,9 +29,13 @@ jobs:
       - name: Setup node and build the repository
         uses: ./amplify-js/.github/actions/node-and-build
 
+      - name: Configure npm authentication
+        run: echo "//registry.npmjs.org/:_authToken=$NPM_TOKEN" >> ~/.npmrc
+        env:
+          NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+
       - name: Publish to @unstable
         working-directory: ./amplify-js
         run: yarn publish:unstable
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          NPM_TOKEN: ${{ secrets.NPM_TOKEN }}