Update build script & Correct browser package

[zhiyuanliang-ms]

This PR does two things:

1. Fix the failure of building packages from FeatureManagement-JavaScript repo in our OOB release pipeline.

I fail to build packages from FeatureManagement-JavaScript repo in our OOB release pipeline. It cannot execute npm install in any subfolders.(There are three packages in the JS FM repo) The log reported connection error: fail to get npm registry.

I rerun the some previous successful attempts, they fail now. After debugging, I found that if we placed the Azure.npmrc in the subfolder, then npm install and npm link can be executed as expected (no connection error any more). The possible reason could be the upgrade of agent major version. Previously, it may allow to fall back the default npm registry. but now it only allows Azure Artifact registry.

Our OOB release pipeline will use Azure Artifact registry by creating a .npmrc file in the root folder. So I update the build script to copy it to each subfolders.

2. Correct the entry point of the browser package. It is an oversight from Fix rollup & package-lock.json #84