[Bug] Cannot search in Chinese string

**Describe the bug**
A clear and concise description of what the bug is.

**To Reproduce**
Steps to reproduce the behavior:
1. Searchbox Cannot search in Chinese string

**Expected behavior**
A clear and concise description of what you expected to happen.

**Context (please complete the following information):**
- OS: Windows
- Docfx version: [e.g. 2.78.5+fafdcd5ddacdb756bd5c4b84f2f07c18292e4821]

**Additional context**
Add any other context about the problem here.

No source file or test is identified. Start by reproducing the searchbox failure with a Chinese query on Windows and trace the search implementation from there. Done means Chinese strings can be found successfully and the behavior is covered by a regression test.

Written by the indexing model from the issue text.