Pre-commit hook doesn't work with custom dart/flutter executable locations

At the moment, the pre-commit hook definition expects `dart`/`flutter` executables to be accessible in the search path.

However, it is a common practice to install several channels on the same machine and use different executable names for them. i.e. `flutter-stable`, `dart-beta`, etc.

It is possible to implement a hook that takes an executable name/path as an argument in the `args` parameter, see https://pre-commit.com/#passing-arguments-to-hooks. However, this requires transforming the definition in the `script` type and using an additional script that would construct the corresponding command to execute. The problem is we cannot just use `bash` for this as Windows users won't be able to use it.