runtime(kdl): include syntax, indent and ftplugin files

closes: #14956

Co-authored-by: Aram Drevekenin <aram@poor.dev>
Signed-off-by: inzuo Jiang <jiangyinzuo@foxmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/indent/kdl.vim

@@ -0,0 +1,26 @@
+" Vim indent file
+" Language:         KDL
+" Author:           Aram Drevekenin <aram@poor.dev>
+" Maintainer:       Yinzuo Jiang <jiangyinzuo@foxmail.com>
+" Last Change:      2024-06-10
+
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+    finish
+endif
+let b:did_indent = 1
+
+setlocal indentexpr=KdlIndent()
+let b:undo_indent = "setlocal indentexpr<"
+
+function! KdlIndent(...)
+  let line = getline(v:lnum)
+  let previousNum = prevnonblank(v:lnum - 1)
+  let previous = getline(previousNum)
+
+  if previous =~ "{" && previous !~ "}" && line !~ "}" && line !~ ":$"
+    return indent(previousNum) + &tabstop
+  else
+    return indent(previousNum)
+  endif
+endfunction