Doc: Improve documentation on JSON#parse and JSON#parse!

Co-authored-by: Bruno Gomes da Silva <brunojabs@gmail.com>

Author: hsbt

ext/json/ext/parser/parser.c

@@ -2950,6 +2950,7 @@ static const char MAYBE_UNUSED(_JSON_nfa_pop_trans)[] = {
 *
 * Parses the current JSON text _source_ and returns the complete data
 * structure as a result.
+* It raises JSON::ParseError if fail to parse.
 */
 static VALUE cParser_parse(VALUE self)
 {

ext/json/ext/parser/parser.rl

@@ -839,6 +839,7 @@ static VALUE cParser_initialize(int argc, VALUE *argv, VALUE self)
  *
  * Parses the current JSON text _source_ and returns the complete data
  * structure as a result.
+ * It raises JSON::ParseError if fail to parse.
  */
 static VALUE cParser_parse(VALUE self)
 {