[Docs] Mention --no-dts somewhere?

Right now there's a `--dts-only` flag that allows tsup to be used to only run `dts`. But I can't find a way to run without `dts` when the config file (`tsup.config.ts`) has `dts: true`. ~~Can that be added in?~~

~~Context: https://github.com/JoshuaKGoldberg/create-typescript-app/issues/1162. I have a repo with a single `tsup.config.ts` that needs to build `.js` files from `.ts` sources before linting. It'd be nice to just run the build using whatever configurations -especially `clean` and `outDir`- are present in `tsup.config.ts`... but not have to incur the speed penalty of type checking.~~

Edit: I just discovered `--no-dts`! But it's not mentioned anywhere on the site. Would you accept a PR mentioning it ...somewhere?

Search the tsup site for the existing --dts-only documentation and identify the most relevant CLI or configuration section. Add a mention of --no-dts there, making clear that it disables declaration generation when enabled in tsup.config.ts; done means the flag is discoverable in the published documentation.

Written by the indexing model from the issue text.