Add wikipedia extra req to README

README.md

@@ -53,6 +53,7 @@ Some components or modules in forte may require some [extra requirements](https:
 * `pip install forte[ner]`: Install packages required for [ner_trainer](https:/asyml/forte/blob/master/forte/trainer/ner_trainer.py)
 * `pip install forte[test]`: Install packages required for running [unit tests](https:/asyml/forte/tree/master/tests).
 * `pip install forte[example]`: Install packages required for running [forte examples](https:/asyml/forte/tree/master/examples).
+* `pip install forte[wikipedia]`: Install packages required for reading [wikipedia datasets](https:/asyml/forte/tree/master/forte/datasets/wikipedia).
 * `pip install forte[augment]`: Install packages required for [data augmentation module](https:/asyml/forte/tree/master/forte/processors/data_augment).
 * `pip install forte[stave]`: Install packages required for [StaveProcessor](https:/asyml/forte/blob/master/forte/processors/stave/stave_processor.py).
 * `pip install forte[audio_ext]`: Install packages required for [AudioReader](https:/asyml/forte/blob/master/forte/data/readers/audio_reader.py).