Generate libaries.json for repository metadata

[suztomo]

For steffnay@ 's system. google-cloud-node's implementation as reference:

• https://github.com/googleapis/google-cloud-node/blob/50c7f821bbf3cb75b44d1d1b7d6cc7642a592be1/libraries.json
• https://github.com/googleapis/google-cloud-node/blob/50c7f821bbf3cb75b44d1d1b7d6cc7642a592be1/bin/generate-readme.mjs#L47.

[meltsufin]

@suztomo Can we get more information on this system that depends on it? Why can't that system do the aggregation?

[suztomo]

Sure.