Auto merge of rust-lang#12913 - anupj:master, r=epage

Updating "features" documentation to add a note about the new limit on number of features

### What does this PR try to resolve?
Adding the following note to [features docs page](https://doc.rust-lang.org/cargo/reference/features.html)

> Note: New crates or versions published on [crates.io](http://crates.io/) are now limited to
> a maximum of 300 features. Exceptions are granted on a case-by-case basis.
> See this [blog post] for details. Participation in solution discussions is
> encouraged via the [crates.io](http://crates.io/) Zulip stream.

### How should we test and review this PR?

I don't think this change requires any additional testing beyond a general review.

### Additional information

src/doc/src/reference/features.md

@@ -7,6 +7,13 @@ either be enabled or disabled. Features for the package being built can be
 enabled on the command-line with flags such as `--features`. Features for
 dependencies can be enabled in the dependency declaration in `Cargo.toml`.
 
+> **Note**: New crates or versions published on crates.io are now limited to
+> a maximum of 300 features. Exceptions are granted on a case-by-case basis.
+> See this [blog post] for details. Participation in solution discussions is
+> encouraged via the crates.io Zulip stream.
+
+[blog post]: https://blog.rust-lang.org/2023/10/26/broken-badges-and-23k-keywords.html
+
 See also the [Features Examples] chapter for some examples of how features can
 be used.