Rollup merge of rust-lang#113249 - tgross35:patch-2, r=jyn514

Document tracking issue for rustdoc `show-type-layout`

Tracking issue: rust-lang#113248

``@rustbot`` label +T-rustdoc +A-docs

Author: matthiaskrgr

src/doc/rustdoc/src/unstable-features.md

@@ -310,6 +310,8 @@ the source.
 
 ### `--show-type-layout`: add a section to each type's docs describing its memory layout
 
+* Tracking issue: [#113248](https://github.com/rust-lang/rust/issues/113248)
+
 Using this flag looks like this:
 
 ```bash