Adding fonts to package via inst/

[jpcompartir]

Make sure package is self-contained and presentations/plots can have custom fonts

Accessed with {systemfonts} + system.file

[jpcompartir]

Add a folder and then make sure it's checked in a .onLoad()

like in:
https://github.com/jpcompartir/LimpiaR/blob/main/R/init.R

[jpcompartir]

Coming in #33