Document how to build a library for SolidJS

My team had difficulties in building a component library for SolidJS because we couldn't find any documentation for it.

We have a monorepo where one package is an application which should use components from another package in the repo.
Each has their own build. We use Vite and vite-plugin-solid to build.

vite-plugin-solid seems to use the package.json exports field with a custom import condition solid.

We couldn't find any documentation about this behavior (if there is one please let me know). Only after scouring through this plugin's source code and the NodeJs docs and looking at existing SolidJS component libs we got some idea about how this works.

IMO it the documentation should answer the following questions:

• How to build a library for solid JS components?
• How to use package.json exports to export SolidJS code
• What's the difference in libraries compared to VDOM Frameworks like React, Vue etc (build done by the application vs build done in each package)
• What's the recommended approach for building in combination with Typescript and/or some CSS preprocessing.

Start with the vite-plugin-solid source, Node.js documentation for package.json exports and the existing SolidJS component libraries mentioned in the issue. Done means adding documentation that explains SolidJS library builds, the solid export condition, application versus package builds, and recommended TypeScript and CSS preprocessing approaches.