Add package.json for github dependency display

[d-b-w]

github has cross-repo dependency visualization. This is an
attempt to add that dependecy information to maeparser. If
it works, I'll also add dependency info to coordgen.

See https://github.com/schrodinger/maeparser/network/dependencies
which is empty, but I think will show something after this is merged.

[ricrogz]

I'm not sure how this will work, I have only seen package.json files in javascript projects, but it is worth a try.

Also, the preferred name seems to be "package-lock.json", according to https://docs.github.com/en/code-security/supply-chain-security/about-the-dependency-graph#supported-package-ecosystems.