fix: reserved field inside group blocks fail parsing

Author: jonathan-ioffe

src/parse.js

@@ -513,6 +513,10 @@ function parse(source, root, options) {
                     parseEnum(type, token);
                     break;
 
+                case "reserved":
+                    readRanges(type.reserved || (type.reserved = []), true);
+                    break;
+
                 /* istanbul ignore next */
                 default:
                     throw illegal(token); // there are no groups with proto3 semantics