Reference the improvement of 2021 panic!

Co-authored-by: Mark Rousskov <[email protected]>

Author: cuviper

posts/2022-01-13-Rust-1.58.0.md

@@ -63,7 +63,10 @@ first, or use the older `name = expression` style of formatting arguments.
 This feature works in all macros accepting format strings. However, one corner
 case is the `panic!` macro in 2015 and 2018 editions, where `panic!("{ident}")`
 is still treated as an unformatted string -- the compiler will warn about this
-not having the intended effect.
+not having the intended effect. Due to the 2021 edition's update of panic
+macros for [improved consistency], this works as expected in 2021 `panic!`.
+
+[improved consistency]: https://doc.rust-lang.org/stable/edition-guide/rust-2021/panic-macro-consistency.html
 
 ### Reduced Windows `Command` search path