cargo-release: update README version

[MCOfficer]

As per #26, this PR makes cargo release replace (or cargo release) replace the version number in the README.

❯ cargo release replace
   Replacing in README.md
--- README.md   original
+++ README.md   replaced
@@ -49 +49 @@
-catppuccin-egui = "4.0"
+catppuccin-egui = "^4.0.0"

warning: aborting release due to dry run; re-run with `--execute`

I didn't check how this fits in with your existing release workflow. cargo-release is capable of pretty much everything a normal crate needs, so I'm not sure where you want to take this idea.

[Stonks3141]

Thanks!