chore: transition from markdown to YAML for issue template

[LangLangBart]

description

Usage of an issue template form written in YAML.

refs

Syntax for issue forms - GitHub Docs

demo

https://github.com/LangLangBart/fzf/issues/new/choose

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Pros

• Validates certain fields, such as fzf version, before filing a report
• Ensures consistency, as every report follows the same format
• …

Cons

• Imposes more restrictions on the user to adhere to a specific format
• …

[junegunn]

Merged, thanks!