Support yofi.toml as config filename

[jdek]

Allows editors to more easily syntax highlight. Didn't open an issue beforehand since this feature is so minor.

[l4l]

Thanks for your contribution, however I would really prefer avoiding that patch as the config path becomes more obscure, e.g having both yofi.config & yofi.toml leads to a troubles in figuring out which one is used. I agree the toml extension would be clearer choice but having two implicit defaults or changing one completely lacks of good motivation so far.

Besides, I suppose 99% of editors allows to specify language/syntax for arbitrary file extensions, doesn't it?

[jdek]

The intention would be to deprecate yofi.config, and then support only yofi.toml after the next major version (1.0.0). To reduce the confusion inside the deprecation period, we could add a warning message similar to what Alacritty and other programs did when moving their configuration files to a more canonical names. This will inform the user exactly which config file being used until the deprecation period ends, when this can be removed again.

The motivation of this patch is to remove the obscurity of using a well-defined configuration format but not its file extension. Whilst most editors do allow you to manually specify the filetype, it requires extra input from the user: It would be nice if things 'just worked'.