Font Library: Add option for (minimal) font stack - at least assignment to the 5 generic font families - to be always W3C compliant

[burnuser]

What problem does this address?

W3C font standards are based on 5 generic font families: serif, sans-serif, cursive, fantasy, monospace
https://www.w3.org/TR/css-fonts-3/#generic-font-families
Having 1 of these 5 as last part in the font stack guarantees a working font display on every device in every browser.
If the loading of primary fonts does not work (connection/server/file/... problems), the system has a working fallback.

In WordPress this (minimal) font stack is not guaranteed at the moment.
Not all theme fonts and not all manually uploaded fonts come with this minimal font stack.
For example in "Twenty Twenty-Four" the included font "Inter" has a working font stack with "sans-serif" as base, but the font "Cardo" has no font stack at all. So, even an actual WordPress standard Theme is not W3C compliant.

What is your proposed solution?

If complete font stack editing is not planned in the near future, add at least a minimal interface option in the Font Library at each font to select the font stack base from the list of the five generic font families.

• Create and use a correct minimal font stack on this base in WordPress.