Document how to use `#[rust_analyzer::completions(...)]`

[BD103]

I just saw #19375 was merged, but I couldn't find any user-facing documentation on how to use #[rust_analyzer::completions(...)]. I did find these comments, but they're within the code:

rust-analyzer/crates/hir-def/src/lib.rs

Lines 1507 to 1527 in 2e1ff25

	// Feature: Completions Attribute
	// Crate authors can opt their type out of completions in some cases.
	// This is done with the `#[rust_analyzer::completions(...)]` attribute.
	//
	// All completeable things support `#[rust_analyzer::completions(ignore_flyimport)]`,
	// which causes the thing to get excluded from flyimport completion. It will still
	// be completed when in scope. This is analogous to the setting `rust-analyzer.completion.autoimport.exclude`
	// with `"type": "always"`.
	//
	// In addition, traits support two more modes: `#[rust_analyzer::completions(ignore_flyimport_methods)]`,
	// which means the trait itself may still be flyimported but its methods won't, and
	// `#[rust_analyzer::completions(ignore_methods)]`, which means the methods won't be completed even when
	// the trait is in scope (but the trait itself may still be completed). The methods will still be completed
	// on `dyn Trait`, `impl Trait` or where the trait is specified in bounds. These modes correspond to
	// the settings `rust-analyzer.completion.autoimport.exclude` with `"type": "methods"` and
	// `rust-analyzer.completion.excludeTraits`, respectively.
	//
	// Malformed attributes will be ignored without warnings.
	//
	// Note that users have no way to override this attribute, so be careful and only include things
	// users definitely do not want to be completed!

Is there a place this can be documented so it is easier to discover and learn about? (I would be willing to open a PR for this, though I may have a few extra questions.) Thank you!

[ChayimFriedman2]

We have a task that extracts // Feature: comments within the code to docs in the manual. Not sure why it's not working here.

[BD103]

We have a task that extracts // Feature: comments within the code to docs in the manual. Not sure why it's not working here.

No it's working, I looked again and found it here! Sorry, I didn't look hard enough :)