flygrep can't seach chinese

## The reproduce ways from Vim starting (Required!)
SPC s b,when i seach whith chinese，there is no result ，when i seach whith english or number ，the result is right。
I guess flygrep doesn't support Chinese search。How can I use Chinese search？


## Screenshots
![图片](https://user-images.githubusercontent.com/32120035/134447438-a54cba14-6398-4e58-813a-3f34aa07d107.png)

![图片](https://user-images.githubusercontent.com/32120035/134447406-3fe2df4c-dfaf-4764-8de3-f3f3f1b2c74d.png)




