Fix missing switch case

`yajl_tok_comment` was not present in the switch case.

Warnings:

```
compiling ../../../../ext/yajl/yajl_lex.c
../../../../ext/yajl/yajl_lex.c:42:13: warning: enumeration value 'yajl_tok_comment' not handled in switch [-Wswitch]
    switch (tok) {
            ^
../../../../ext/yajl/yajl_lex.c:42:13: note: add missing switch cases
    switch (tok) {
            ^
```

Co-authored-by: John Hawthorn <john@hawthorn.email>

ext/yajl/yajl_lex.c

@@ -43,6 +43,7 @@ const char *yajl_tok_name(yajl_tok tok) {
         case yajl_tok_bool: return "bool";
         case yajl_tok_colon: return "colon";
         case yajl_tok_comma: return "comma";
+        case yajl_tok_comment: return "comment";
         case yajl_tok_eof: return "eof";
         case yajl_tok_error: return "error";
         case yajl_tok_left_brace: return "open_array";