Consider removing the plugins array and how to document target option

[Murderlon]

Initial checklist

• I understand this is a feature request and questions should be posted in the Community Forum
• I searched issues and couldn’t find anything (or linked relevant results below)

Problem

Sometime ago we landed #4343, to auto discover and install plugins without target. We haven't updated the docs on this yet. We should also decide whether plugins can be removed in the major.

Solution

• Remove plugins
• Document you do not need target if you use Dashboard and update all examples to look more clean.

Alternatives

Only deprecate plugins. But if everything continues to work without it automatically, there would need to be an edge case to justify this.

[Murderlon]

@arturi can you recall a reason why we wouldn't want to remove plugins?

[arturi]

1. I think we just weren't sure there was a better way than plugins — now there is.
2. For backwards-compat, some people might be using it conditionally, like you have 5 plugins available in Uppy, but only 2 actually rendered.

Sounds like it’s fine to remove in 4.0 (and add back in a minor in case of a major screw up).