[FEAT] Determine font names from the aliases "serif", "sans-serif", "monospace"

### Description

Many people use these standard aliases in fontconfig to set their fonts system-wide. Fastfetch only displays the aliases. The real font names can easily be determined. For example, with a command like `fc-match -s ':family=monospace'`.

### Motivation

It's an enhancement to existing font fields.

### Additional context

Start by tracing how Fastfetch currently obtains and displays its font fields, then inspect how fontconfig can resolve the serif, sans-serif, and monospace aliases. Use `fc-match -s ':family=monospace'` as the reference check, and confirm that the displayed values are real font names rather than the aliases.

Scritto dal modello di indicizzazione a partire dal testo della issue.