Rollup merge of #81835 - jesusprubio:improve-long-eplanation-e0546, r=GuillaumeGomez

Improve long explanation for E0546

Helps with #61137

Author: GuillaumeGomez

compiler/rustc_error_codes/src/error_codes/E0546.md

@@ -1,4 +1,4 @@
-A feature name is missing.
+The `feature` value is missing in a stability attribute.
 
 Erroneous code example:
 
@@ -13,7 +13,7 @@ fn unstable_fn() {}
 fn stable_fn() {}
 ```
 
-To fix the issue you need to provide a feature name.
+To fix the issue you need to provide the `feature` field.
 
 ```
 #![feature(staged_api)]
@@ -25,3 +25,10 @@ fn unstable_fn() {}
 #[stable(feature = "stable_fn", since = "1.0.0")] // ok!
 fn stable_fn() {}
 ```
+
+See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix
+of the Book and the [Stability attributes][stability-attributes] section of the
+Rustc Dev Guide for more details.
+
+[how-rust-made-nightly]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html
+[stability-attributes]: https://rustc-dev-guide.rust-lang.org/stability.html