Merge pull request #1059 from yt605155624/fix_docs

add readme

demos/style_fs2/README.md

+# Style FastSpeech2
+You can change the `pitch`、`duration` and `energy` of `FastSpeech2`.
+
+Run the following command line to get started:
+```
+./run.sh
+```
+For more details, please see `style_syn.py`