Move admonitions to the contributor guide

Author: ehuss

contributor-guide/src/SUMMARY.md

@@ -9,7 +9,7 @@
 - [Tests]()
 - [Formatting](formatting/index.md)
     - [Markdown](formatting/markdown.md)
-    - [Admonitions]()
+    - [Admonitions](formatting/admonitions.md)
 - [Language rules]()
     - [rustc test annotations]()
 - [Examples]()

contributor-guide/src/formatting/admonitions.md

@@ -0,0 +1,23 @@
+# Admonitions
+
+[`mdbook-spec`](../tooling/mdbook-spec.md) provides admonitions which use a style similar to GitHub-flavored markdown. The style name is placed at the beginning of a blockquote, such as:
+
+```markdown
+> [!WARNING]
+> This is a warning.
+
+> [!NOTE]
+> This is a note.
+
+> [!EDITION-2024]
+> This is an edition-specific difference.
+
+> [!EXAMPLE]
+> This is an example.
+```
+
+The color and styling is defined in [`theme/reference.css`](https://github.com/rust-lang/reference/blob/master/theme/reference.css) and the transformation and icons are in [`mdbook-spec/src/admonitions.rs`](https://github.com/rust-lang/reference/blob/HEAD/mdbook-spec/src/admonitions.rs).
+
+See the [conventions section] for a description of how these should be used.
+
+[conventions section]: https://doc.rust-lang.org/nightly/reference/#conventions

docs/authoring.md

@@ -141,26 +141,6 @@ When running into a rustdoc limitation, consider manually linking to the correct
 
 [intra]: https://doc.rust-lang.org/rustdoc/write-documentation/linking-to-items-by-name.html
 
-### Admonitions
-
-Admonitions use a style similar to GitHub-flavored markdown, where the style name is placed at the beginning of a blockquote, such as:
-
-```markdown
-> [!WARNING]
-> This is a warning.
-
-> [!NOTE]
-> This is a note.
-
-> [!EDITION-2024]
-> This is an edition-specific difference.
-
-> [!EXAMPLE]
-> This is an example.
-```
-
-The color and styling is defined in [`theme/reference.css`](https://github.com/rust-lang/reference/blob/master/theme/reference.css) and the transformation and icons are in [`mdbook-spec/src/admonitions.rs`](https://github.com/rust-lang/reference/blob/HEAD/mdbook-spec/src/admonitions.rs).
-
 ## Style
 
 Idioms and styling: