feature request: Add documentation for events and formatter.format option

[aShabat]

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Describe the feature

Can you add documentation for ConformCommandPre and ConformCommandPost events and for formatters.[name].format option?
I understand that format option is not intended for active use, but you wrote about it in #186, so it would be nice to have some explanation.

Provide background

I was looking at a way to run mini.align as a formatter. Both events and format option provide a way to do that, but I had to dig a bit to find them.

What is the significance of this feature?

nice to have

Additional details

No response

[stevearc]

These are niche topics that I would actually want to steer the average user away from. If someone wants to make a PR to add some docs under the "advanced topics" section or similar, I would review it.