Add Kotlin Support using ktlint formatter

[A1Liu]

ktlint (https://github.com/pinterest/ktlint) can format Kotlin code, and it'd be nice to have it integrated into codefmt.

[AhmadNaruto]

waiting to supported.

[dbarnett]

Should be pretty straightforward to integrate, but nope, nobody's done it yet. I haven't used ktlint myself and won't be able to work on it, but pull requests are very welcome!