Migrate Alacritty configuration to TOML

[tacerus]

YAML configuration is deprecated as of Alacritty version 0.13.0.

Resolve this banner for new users:

Users with a custom Alacritty/Sway configuration need to migrate and update on their own, I think it is not a good idea to call the migration in a post script as users might have more complex YAML configurations.

See https://github.com/alacritty/alacritty/issues/6592.

[FilippoBonazziSUSE]

Thanks for the PR

[tacerus]

Thanks for merging. :)