Fix parsing of options

[tonda-kriz]

support also this syntax

option (google.api.http) = {
    custom: {
        kind: "FETCH"
        path: "/foo/bar/baz/{id}"
    }
    additional_bindings: [
      {
          get: "/foo/bar/baz/{id}"
      },
      {
          post: "/foo/bar/baz/"
          body: "*"
      }
    ]
};

ref: https://protobuf.com/docs/language-spec#options