Idea: public assets for packages

[mbeckem]

Existing assets/** are published with a package but must be imported (e.g. import url from "./foo?url") to be included in the build.

It would be nice to have an additonal public directory (like the global vite public directory) whose files will always be copied over, no matter whether they're imported or not (e.g. packageA/public/foo.txt --> packageA/foo.txt in dist).