chore: switch to edition 2021 (#131)

Author: toku-sa-n

CHANGELOG.md

@@ -5,6 +5,9 @@
 - License and contribution notes are added to the README.
 - Dependabot is enabled.
 
+### Changed
+- Switched to Rust edition 2021.
+
 ### Fixed
 - Outdated code example in `README.md` is fixed.
 - Removed all the use of deprecated code.

Cargo.toml

@@ -2,7 +2,7 @@
 name = "xhci"
 version = "0.8.2"
 authors = ["Hiroki Tokunaga <[email protected]>"]
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "A library to handle xHCI"
 repository = "https://github.com/rust-osdev/xhci"