Update Changelog and Readme

Add Changelog entry for the `PinInitable` trait and document the
`unsafe-pinned` feature in the Readme.

Signed-off-by: Christian Schrefl <chrisi.schrefl@gmail.com>

Author: onestacked

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- `PinInitable` trait added for creating wrapper structs with a structurally pinned value.
 - `InPlaceInit` now only exists when the `alloc` or `std` features are enabled
 
 ## [0.0.9] - 2024-12-02

README.md

@@ -40,6 +40,10 @@ However, using the crate on stable compilers is possible by disabling `alloc`. I
 will require the `std` feature, because stable compilers have neither `Box` nor `Arc` in no-std
 mode.
 
+### Nightly needed for `unsafe-pinned` feature
+
+This feature enables the `PinInitable` implementation on the unstable `core::pin::UnsafePinned` type. This requires the [`unsafe_pinned` unstable feature](https://github.com/rust-lang/rust/issues/125735) and therefore a nightly compiler. Note that this feature is not enabled by default.
+
 ## Overview
 
 To initialize a `struct` with an in-place constructor you will need two things: