custom backend support (mostly impossible)

[sctech-tr]

Is your feature request related to a problem? Please describe.
there are LOTS of fetch programs out there, and i'm sure there are people wanting their fetch programs to be supported as backends, (or it's just me) but this is way confusing to make.

Describe the solution you'd like
if hyfetch also supports distro ascii arts built-in, (i didn't go search for it in the code) (EDIT: i did it's there) potentially we could add support for custom backends that match some criterias.

Describe alternatives you've considered
uhh i didn't

Additional context
this is not critical or must-have, it would just be nice