chore: create xml highlights

[mikesmithgh]

-- xml xmlTag = { link = "GruvboxAquaBold" }, xmlEndTag = { link = "GruvboxAquaBold" }, xmlTagName = { link = "GruvboxBlue" }, xmlEqual = { link = "GruvboxBlue" }, docbkKeyword = { link = "GruvboxAquaBold" }, xmlDocTypeDecl = { link = "GruvboxGray" }, xmlDocTypeKeyword = { link = "GruvboxPurple" }, xmlCdataStart = { link = "GruvboxGray" }, xmlCdataCdata = { link = "GruvboxPurple" }, dtdFunction = { link = "GruvboxGray" }, dtdTagName = { link = "GruvboxPurple" }, xmlAttrib = { link = "GruvboxOrange" }, xmlProcessingDelim = { link = "GruvboxGray" }, dtdParamEntityPunct = { link = "GruvboxGray" }, dtdParamEntityDPunct = { link = "GruvboxGray" }, xmlAttribPunct = { link = "GruvboxGray" }, xmlEntity = { link = "GruvboxRed" }, xmlEntityPunct = { link = "GruvboxRed" },