Improve collect package data for error handling

[huang-benny]

We want to be more detailed in the fail response.

cdk-construct-analyzer https://github.com/cdklabs/cdk-pipelines-github cdk-construct-analyzer cdklabs/cdk-pipelines-github

Instead of 'no repository URL found in NPM data', maybe we can fail with a better error, or even provide a suggestion like "did you mean just 'cdk-pipelines-github'"