Add attributes.codegen.inline.trait
This adds some wording that was removed from the "optimization hints"
section.
diff --git a/src/attributes/codegen.md b/src/attributes/codegen.md
index 21a2853..ccc9477 100644
--- a/src/attributes/codegen.md
+++ b/src/attributes/codegen.md
@@ -62,6 +62,9 @@
> [!NOTE]
> `#[inline]` in every form is a hint, with no *requirements* on the language to place a copy of the attributed function in the caller.
+r[attributes.codegen.inline.trait]
+When `inline` is applied to a function in a [trait definition], it applies only to that function when used as a default function for a trait implementation and not to all trait implementations.
+
r[attributes.codegen.cold]
### The `cold` attribute
