[bulkImportPerformers] Encoding error in Chinese and some unexpected errors

[Kami958]

It will be an error ‘gbk‘ codec can‘t decode if the performers.txt includes chinese(UTF-8).

The solution is to modify the reading function in performers.py with encoding="utf-8".

Some unexpected errors:

1. It doesn't work when launched from the Tasks page. In the logs, it reports that it cant find Python. I've indeed installed Python (also configured the system variables) and stashapp-tools. However, it works fine when I manually execute it using Python.
   It is my first time to use Stash. Did I miss some configurations?

2. GRAPHQL_VALIDATION_FAILED I didn't know that I had to generate an API key, and I fixed that already.