better resolution for third party adapters

[paperclover]

the issue is AdapterData requires an exact path to the adapter, which for purplet's adapters, we use @rollup/plugin-url to copy these into the build directory, then do some magic. i dont want to force that on third party devs.

ideally, package-name/some/entrypoint.ts should resolve to where you'd expect it to, without having to configure package.json stuff so that require.resolve() works. or maybe even some way it can be a relative file.

not sure. it's a really complicated situation