Documentation for UpdateResult

[mjomble]

InsertResult is very well documented, with the nuances of different dialects clearly described 👍

UpdateResult, however, contains only two similarly named fields (numUpdatedRows and numChangedRows) with zero comments, which can lead to some confusion 😄

It would be nice to have similarly detailed comments in both. Unfortunately, I don't have enough information to properly document this myself in a PR. I found some info in this issue, but I suspect there's more to it.

Maybe @wirekang, @igalklebanov or @koskimas would be up for it? Or you could post the necessary information in this thread, which I could then prepare into a PR.

[wirekang]

Comments on QueryResult will be enough information to make a PR. Good luck.

kysely/src/driver/database-connection.ts

Lines 23 to 35 in deea8e2

	/**
	* This is defined for insert, update, delete and merge queries and contains
	* the number of rows the query inserted/updated/deleted.
	*/
	readonly numAffectedRows?: bigint
	/**
	* This is defined for update queries and contains the number of rows
	* the query changed.
	* This is optional and only provided by some drivers like node-mysql2.
	*/
	readonly numChangedRows?: bigint