Update Changes section in README.md

Update README.md for v0.4.3 release

- Document that as_<int_type> is now a `const` function if the `Copy` trait is derived on enum.

Refactor error handling and improve pretty print generation

- Enhance error message formatting for invalid IntType
- Create a new LitStr for pretty print body

Merge pull request #3

Fixed the cfg warning and bump version to 0.4.1

Merge pull request #2 from cubicle-jockey/v0.4.0

V0.4.0

Merge remote-tracking branch 'origin/master'

Update enum_ext and proc-macro2 dependencies

The enum_ext dependency has been updated from version 0.2.1 to 0.2.2 in both README.md and Cargo.toml. Similarly, the version of proc-macro2 has also been updated in the Cargo.toml file from 1.0.83 to 1.0.84.

Update enum_ext version to 0.2.1

This commit includes a version bump of the `enum_ext` dependency in both the README.md and Cargo.toml files from version 0.2.0 to 0.2.1.

Revised the docs

Bumped the version