Add changelog entry for #7664

Author: robamler

CHANGELOG.md

@@ -63,6 +63,7 @@ Naga now infers the correct binding layout when a resource appears only in an as
 - Apply necessary automatic conversions to the `value` argument of `textureStore`. By @jimblandy in [#7567](https://github.com/gfx-rs/wgpu/pull/7567).
 - Properly apply WGSL's automatic conversions to the arguments to texture sampling functions. By @jimblandy in [#7548](https://github.com/gfx-rs/wgpu/pull/7548).
 - Properly evaluate `abs(most negative abstract int)`. By @jimblandy in [#7507](https://github.com/gfx-rs/wgpu/pull/7507).
+- Generate vectorized code for `[un]pack4x{I,U}8[Clamp]` on SPIR-V and MSL 2.1+. By @robamler in [#7664](https://github.com/gfx-rs/wgpu/pull/7664).
 
 #### DX12