✨ Support fallback fonts in Text Editing preferences

### Is your feature request related to a problem? Please describe.

No

### Describe the solution you'd like

Hello,

Currently, the **Text Editing** settings allow users to select one font only. In many cases, one font is not enough to cover up the Unicode characters that need. We could use multiple fonts to work as a font chain, just like the CSS `font-family`.

In Cocoa, there is a way to combine multple fonts as one NSFont instance, sample code:

~~~swift
static func combinedFont(from fontNames: [String], size: CGFloat) -> NSFont? {
guard let primary = fontNames.first, let primaryFont = NSFont(name: primary, size: size) else { return nil }
let primaryDescriptor: NSFontDescriptor = primaryFont.fontDescriptor
let descriptors: [NSFontDescriptor] = fontNames.dropFirst().map { name -> NSFontDescriptor in
return primaryDescriptor.addingAttributes([.name: name])
}
let descriptor: NSFontDescriptor = primaryDescriptor.addingAttributes([.cascadeList: descriptors])
return NSFont(descriptor: descriptor, size: size)
}
~~~

### Describe alternatives you've considered

Maybe we could put a TextField in **Text Editing** settings, let users to enter the font names they wanted.

### Additional context

Start by inspecting the Text Editing preferences and how the editor currently applies its single selected font. Review the provided Cocoa NSFont cascadeList example and consider the TextField alternative for entering font names. Done should mean users can configure multiple fallback fonts and see Unicode characters rendered through the font chain.

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