Automatically generate docs from component definitions

[langestefan]

I've been going through the code / docs quite a bit these past few days, because I'm adding some components I need.

Is your feature request related to a problem? Please describe.

Some components have no documentation (HeatingResistor for example), some components have incomplete documentation. Fields like states and connectors are manually typed and there is no standardization in how those parts of the docs are formatted. This makes it more difficult to find what you need.

Describe the solution you’d like

Instead of manually putting docstrings at the top of component definitions I suggest we directly generate documentation from the fields inside @mtkmodel. In particular description, bounds, guess, unit and any other fields that are available from the metadata: Symbolic Metadata. This avoids the need to type everything twice. We can still have a docstring at the top with a broader description. The fields can be automatically generated and put in a table for example.

This is an example of what I would like to achieve: https://developers.home-assistant.io/docs/core/entity/number