Expose a C method to parse type parameters.

This is useful to parse a "class signature" such as this:

```rb
\#: [in A, B = String, out < Object]
class Foo; end
```

Signed-off-by: Alexandre Terrasa <alexandre.terrasa@shopify.com>

Author: Morriar

include/rbs/parser.h

@@ -130,6 +130,8 @@ bool rbs_parse_type(rbs_parser_t *parser, rbs_node_t **type);
 bool rbs_parse_method_type(rbs_parser_t *parser, rbs_method_type_t **method_type);
 bool rbs_parse_signature(rbs_parser_t *parser, rbs_signature_t **signature);
 
+bool rbs_parse_type_params(rbs_parser_t *parser, bool module_type_params, rbs_node_list_t **params);
+
 /**
  * Parse an inline leading annotation from a string.
  *

src/parser.c

@@ -3258,6 +3258,19 @@ bool rbs_parse_signature(rbs_parser_t *parser, rbs_signature_t **signature) {
   return true;
 }
 
+bool rbs_parse_type_params(rbs_parser_t *parser, bool module_type_params, rbs_node_list_t **params) {
+  if (parser->next_token.type != pLBRACKET) {
+    rbs_parser_set_error(parser, parser->next_token, true, "expected a token `pLBRACKET`");
+    return false;
+  }
+
+  rbs_range_t rg = NULL_RANGE;
+  rbs_parser_push_typevar_table(parser, true);
+  bool res = parse_type_params(parser, &rg, module_type_params, params);
+  rbs_parser_push_typevar_table(parser, false);
+  return res;
+}
+
 id_table *alloc_empty_table(rbs_allocator_t *allocator) {
   id_table *table = rbs_allocator_alloc(allocator, id_table);