runtime(kotlin): Add Kotlin runtime files (#13110)

Closes udalov/kotlin-vim#39

Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/ftplugin/kotlin.vim

@@ -0,0 +1,33 @@
+" Vim filetype plugin file
+" Language:     Kotlin
+" Maintainer:   Alexander Udalov
+" URL:          https://github.com/udalov/kotlin-vim
+" Last Change:  7 November 2021
+"               2023 Sep 17 by Vim Project (browsefilter)
+
+if exists('b:did_ftplugin') | finish | endif
+let b:did_ftplugin = 1
+
+let s:save_cpo = &cpo
+set cpo&vim
+
+setlocal comments=sO:*\ -,mO:*\ \ ,exO:*/,s1:/*,mb:*,ex:*/,://
+setlocal commentstring=//\ %s
+
+setlocal formatoptions-=t formatoptions+=croqnl
+silent! setlocal formatoptions+=j
+
+setlocal includeexpr=substitute(v:fname,'\\.','/','g')
+setlocal suffixesadd=.kt
+
+let b:undo_ftplugin = "setlocal comments< commentstring< ".
+    \ "formatoptions< includeexpr< suffixesadd<"
+
+if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
+  let b:browsefilter = "Kotlin Source Files (*.kt, *kts)\t*.kt;*.kts\n" .
+	\ "All Files (*.*)\t*.*\n"
+  let b:undo_ftplugin .= " | unlet! b:browsefilter"
+endif
+
+let &cpo = s:save_cpo
+unlet s:save_cpo