[Feature Request] Improve documentation for custom elements

[mediabeastnz]

Description

I've had to make a few custom elements on a couple projects recently and the experience wasn't the best. The documentation points you in the right direction but basically stops and says copy one of Crafts existing elements.

It would be great if a simple element could be created more quickly either with better documentation e.g. actual examples or some kind of CLI tool.

Even if the docs are for a really simple element e.g. form submissions.