Update src/query.md

Co-authored-by: Boxy <rust@boxyuwu.dev>

Author: xizheyin

src/query.md

@@ -170,6 +170,7 @@ pub fn provide(providers: &mut rustc_middle::util::Providers) {
 Note that `util::Providers` implements `DerefMut` to `query::Providers` so callers of the `provide` functions can pass in a `util::Providers` and it will just work for provider functions that accept `query::Providers` too
 
 - This function takes a mutable reference to the `Providers` struct and sets the fields to point to the correct provider functions.
+- You can also assign queries individually, e.g. `providers.type_of = type_of;`.
 - You can assign fields individually for each provider type (local, external, and hooks).
 
 #### Adding a new provider