Kakoune: Add rustfmt to filetype

[pickfire]

Steps

Need to manually add to config from what is shown in wiki https://github.com/mawww/kakoune/wiki/Languages.

hook global WinSetOption filetype=rust %{
  set window formatcmd 'rustfmt'
}

Outcome

Nothing but need to manually add formatcmd

Expected

Rust filetype are expected to use rustfmt by default. Possible to add it to https://github.com/mawww/kakoune?

[Delapouite]

Same could be done for gofmt I think. These 2 tools are standards in their respective ecosystem.

[andreyorst]

I think that c-family can test if either clang-format or another supported formatter is installed and set formatcmd accordingly.

[maximbaz]

@Delapouite not sure about gofmt being standard, there's also goimports 😉

[mawww]

This is now fixed.

[pickfire]

@Delapouite @andreyorst I had already added for rust, feel free to add one for go and c. (I need to fix the wiki as well)