Add NPM_TOKEN to the npmrc configuration to be able to publish the npm package from circleci

Reviewed By: mjesun

Differential Revision: D7586241

fbshipit-source-id: eaba25453c1aca00c07bf0eae961878e1de2e391

circle.yml

@@ -78,6 +78,8 @@ jobs:
           working_directory: packages/metro
           command: yarn --no-progress
       - save-cache: *save-cache
+      - run:
+          command: echo "//registry.npmjs.org/:_authToken=$NPM_TOKEN" >> ~/.npmrc
       - run:
           working_directory: ~/metro
           command: npm run publish