Rollup merge of #85334 - r00ster91:patch-8, r=dtolnay

Add doc aliases to `unit`

I think it makes sense for `unit` to have the same doc aliases as `tuple` does.

Author: Dylan-DPC

library/std/src/primitive_docs.rs

@@ -345,6 +345,9 @@ mod prim_never {}
 mod prim_char {}
 
 #[doc(primitive = "unit")]
+#[doc(alias = "(")]
+#[doc(alias = ")")]
+#[doc(alias = "()")]
 //
 /// The `()` type, also called "unit".
 ///