Mention new #[codec(crate = ...)] attribute for MaxEncodedLen derive (#275)

* Mention new #[codec(crate = ...)] attribute for MaxEncodedLen derive

* Update CHANGELOG.md

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Update CHANGELOG.md

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Author: 3 people

CHANGELOG.md

@@ -10,6 +10,9 @@ and this crate adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.h
 
 ### Added
 - `MaxEncodedLen` trait for items that have a statically known maximum encoded size. ([#268](https://github.com/paritytech/parity-scale-codec/pull/268))
+- `#[codec(crate = "<path>")]` top-level attribute to be used with the new `MaxEncodedLen`
+trait, which allows to specify a different path to the crate that contains the `MaxEncodedLen` trait.
+Useful when using generating a type through a macro and this type should implement `MaxEncodedLen` and the final crate doesn't have `parity-scale-codec` as dependency.
 
 ## [2.1.3] - 2021-06-14