chore(cargo): append ".toml" to config

[Rudxain]

This mutes the following message from cargo check

warning: `.cargo/config` is deprecated in favor of `config.toml`
note: if you need to support cargo 1.38 or earlier, you can symlink `config` to `config.toml`

[deepsource-io]

Here's the code health analysis summary for commits 84b2363..594eeed. View details on DeepSource ↗.

Analysis Summary

Analyzer	Status	Summary	Link
Rust	✅ Success		View Check ↗
Test coverage	⚠️ Artifact not reported	Timed out: Artifact was never reported	View Check ↗

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