This replaces the xml highlighter with one that supports inner lua strings. This is for editing OpenITG/NotITG/Stepmania .xml files that have embedded lua.
If you use vim-plug, you can install by adding this to your init.vim:
Plug 'XeroOl/xml-lua.vim'Or similar for other plugin managers.
Otherwise, just add the syntax/xml.vim file into your vim's syntax folder.