2024 edition support

The 2024 edition does not seem to be supported:

```console
$ cargo-checkct init -d .
Error: Failed to find the cargo manifest at: "."

Caused by:
    TOML parse error at line 16, column 11
       |
    16 | edition = "2024"
       |           ^^^^^^
    data did not match any variant of untagged enum MaybeInherited
```