Add KDL syntax highlighting

[adsick]

Hi, thanks for the program, I use it daily.
In case you don't know about KDL you can learn about it at https://kdl.dev/

[keith-hall]

It looks like there is already a package you can use: https://packagecontrol.io/packages/KDL

obviously the installation instructions there are for Sublime Text via Package Control so don't apply to bat - https://github.com/sharkdp/bat/blob/master/README.md#adding-new-syntaxes--language-definitions should help

side note: to my untrained eye, KDL syntax looks similar to Groovy, you might find that Groovy syntax highlighting works well