Allow unicode chars in tipuesearch_content.json

The file `tipuesearch_content.json` has utf-8 encoding and contains Unicode text. It does not make sense to enforce only ascii-characters in it, which is the default setting of `json.dump()`. This also has a downside of increasing the size of the by 160% in case of Russian texts (from 500kB to 1300kB) -- a serious problem for the target use case.

This pull request allows Unicode text to be present in   `tipuesearch_content.json`