Add function for getting just the yaml key into the winbar

[joshzcold]

get_yaml_key_and_value can be distracting with large yaml values, so this is another option for those that might want it

[joshzcold]

Helps out when the value would be unreable in the winbar.

just using get_yaml_key is much easier to process.

[cuducos]

Hi : ) I think you need to rebase your branch. I see some outdated bits on the README.me (section headings, for example), and in the Lua file (e.g. assure_yaml_filetype is now gone in the main branch)… would you mind double-checking this, please? Otherwise, if you allow, I can merge that to a feature branch and work on it myself instead.

[joshzcold]

Done, thank you 👍

[cuducos]

Thank you so much 💜