add a default font (#8445)

# Objective

- Have a default font

## Solution

- Add a font based on FiraMono containing only ASCII characters and use
it as the default font
- It is behind a feature `default_font` enabled by default
- I also updated examples to use it, but not UI examples to still show
how to use a custom font

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## Changelog

* If you display text without using the default handle provided by
`TextStyle`, the text will be displayed