Support Kotlin language

[DonZheng]

@shuzijun Kotlin is getting its steam in the mobile dev community. Got any plan to update your lovely plugin for it? Cheers

[ehnait]

有计划支持Kotiln吗？

[shuzijun]

We tried to add parsing, but there are too few documents. Those who know the syntax better can continue to develop based on this branch.

https://github.com/shuzijun/plantuml-parser/tree/feat/kt