Add missing Lua keyword (ilai-deutel#277)

syntax.d/lua.ini

@@ -6,5 +6,5 @@ singleline_string_quotes="
 singleline_comment_start=--
 multiline_comment_delims=--[[, --]]
 multiline_string_delim="
-; https://www.lua.org/pil/1.3.html
-keywords_1=and, break, do, else, elseif, end, false, for, function, if, in, local, nil, not, or, repeat, return, then, true, until, while
+; https://lua.org/manual/5.4/manual.html#3.1
+keywords_1=and, break, do, else, elseif, end, false, for, function, goto, if, in, local, nil, not, or, repeat, return, then, true, until, while