Terminal: Allow for the configuration of font fallback

[onceSS]

I am a Chinese developer, sometimes I have to use Chinese, or my Chinese version system will display some prompts in Chinese.

However, this terminal cannot specify multiple fonts in setting, for example: "editor.fontFamily": "DejaVu Sans Mono, Noto Sans CJK SC"(an example from vscode).

I hope this terminal can support multiple fonts setting in the future, thank you.

[phuclv90]

I don't think you need to specify different fonts. Regardless of any locale you use, Chinese characters can always be displayed properly because there are font substitution, font linking and font fallback behind the scenes

[mdtauk]

Fonts in the JSON file could be an array, like with CSS, where if a font is not available, or maybe even per glyph - it goes to the next font listed, and falls back.

[DHowett-MSFT]

This will be part of #1790.

[mariusstrom]

Adding the word fontFace in here to make it easier to find this issue.

[mariusstrom]

It would be nice if VS Code and Terminal were more consistent on configuration parameters as well. This is a bigger problem, but this is a good example: vscode uses fontFamily, Terminal uses fontFace as the configuration parameter.