add ":f" as an alias for ":fmt/:format"

[samankittani]

:f isn't used for anything, and ":fmt" is a bit cumbersome. This would be better suited as a custom command, but that isn't possible yet (#4423). It would be nice to have ":fw" and ":fwq" to format-write and format-write-quit.

[Rudxain]

I'm unsure if this is worth it:

• If a user has auto-format = true in their languages.toml, then they wouldn't need the cmd (unless they want to reduce writes to storage).
• If auto-format = false for some lang, then they only want to fmt some (or none) files. In that case, they can simply :set-option auto-format = true whenever they open a file they want to fmt.
• If a user really dislikes auto-format (maybe because it's distracting?), then they would rarely ever fmt manually. Maybe they use a tool that formats all files in a repo before commit, rather than fmt while the editor is open.

However, those 3 points assume the buffer is associated with a file.

Sometimes, it makes sense to view/edit a buffer without ever writing it to the file-system. Pasting into a buffer is one of those cases.