Extract lua language support into an extension (#10437)

Release Notes:

- Extracted lua language support into an extension, and improved Lua
highlighting and completion label styling.

---------

Co-authored-by: Marshall <marshall@zed.dev>

extensions/lua/languages/lua/indents.scm

@@ -0,0 +1,10 @@
+(if_statement "end" @end) @indent
+(do_statement "end" @end) @indent
+(while_statement "end" @end) @indent
+(for_statement "end" @end) @indent
+(repeat_statement "until" @end) @indent
+(function_declaration "end" @end) @indent
+
+(_ "[" "]" @end) @indent
+(_ "{" "}" @end) @indent
+(_ "(" ")" @end) @indent