Document dist-custom-elements output target

[markacianfrani]

Stencil version:

 @stencil/core@<any>

I'm submitting a: [x] feature request

Provide documentation on the dist-custom-elements output target. This is a really useful feature that is undocumented. So far I've found it leads to a way smaller bundle size and provides a lighter weight option for users to cherry pick individual components.

Questions to consider:

• How does this differ from dist-custom-elements-bundle? (the naming is definitely super confusing)
• What are some real world use cases? (looks like Ionic has an experimental build that's using it?)
• What are the trade offs? When shouldn't I use this? I'm guessing that each component imports some things from stencil core so it might be inefficient if you're cherry picking a bunch of components?

Additional considerations:

Is dist-custom-elements supposed to used in the Vue output target? The docs mentioned this:

customElementsDir
This is the directory where the custom elements are imported from when using the [Custom Elements Bundle](https://stenciljs.com/docs/custom-elements). Defaults to the components directory. Only applies when includeImportCustomElements is true.

the components directory is the default directory of the dist-custom-elements output target. which makes me think that it was meant for this target. Either way, it works flawlessly with it.

[rwaskiewicz]

Thanks for this! We're going to be looking into this in the near future, although I can't give an exact timeline just yet. In the mean time, I'm going to move this to the stencil site repository, as that's where our documentation lives today. Thanks again!

[splitinfinities]

This is complete! https://stenciljs.com/docs/custom-elements