Add cargo fmt pre-commit hook

[google-labs-jules]

Added a .pre-commit-config.yaml file to the repository root.
This configuration sets up a local pre-commit hook that runs cargo fmt on the implants workspace (using the --manifest-path implants/Cargo.toml argument) whenever a commit is made.
This helps maintain code style consistency across the Rust codebase.

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PR created automatically by Jules for task 6095698882223920716 started by @KCarretto

[google-labs-jules]

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