Bump bytemuck from 1.13.1 to 1.21.0

Bumps [bytemuck](https://github.com/Lokathor/bytemuck) from 1.13.1 to 1.21.0.
- [Changelog](https://github.com/Lokathor/bytemuck/blob/main/changelog.md)
- [Commits](Lokathor/bytemuck@v1.13.1...v1.21.0)

---
updated-dependencies:
- dependency-name: bytemuck
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -12,7 +12,7 @@ repository = "https://github.com/virtualritz/glyphana/"
 
 [dependencies]
 ahash = "0.8.3"
-bytemuck = "1.13.1"
+bytemuck = "1.21.0"
 eframe = { version = "0.22", default-features = false, features = [
     #"accesskit",     # Make egui comptaible with screen readers. NOTE: adds a lot of dependencies.
     "default_fonts", # Embed the default egui fonts.