UI: Font-Family Should be configable

**Describe the bug**
Some characters are not displayed properly. Because bindiff trying to use `Roboto Mono` as the only font, However this font family doesn't support non-ASCII characters. Maybe font-family config can be add into `config>main settings>general` card.

**To Reproduce**
Just Open it and open any config window.

**Screenshots**

**Environment (please complete the following information):**
- OS and version: Windows 10
- Locale: zh-CN (Simplified Chinese)
- Disassembler and version: IDA Pro 7.1

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