Make font setting functions more fault-tolerant

[rye]

As it stands, the font setting functions are not fault-tolerant at all. If a font does not exist on the system, there is simply no error except the one raised by Emacs itself, which then halts the init process. For instance, the default font in my configuration is Fira Code, but this font is not installed on some machines that I work on, and I have to make local changes to my configuration to prevent a failure in loading.

I intend to work on this one—it will involve defining a pre-defined font hierarchy alist—as users add fonts, they can prepend to this list cons cells of the form ("Font Family Name" . default-size). We can also write defuns for interacting with this list.

[rye]

Code Snippet from IELM using x-list-fonts

Here's a basic snippet of code to see how this might get implemented basically.

A better example using find-font