See also #73, register_font() can be expensive becuas:
> system.time(systemfonts::system_fonts())
user system elapsed
0.682 0.113 1.032
> system.time(systemfonts::system_fonts())
user system elapsed
0.010 0.001 0.013
> system.time(systemfonts::system_fonts())
user system elapsed
0.012 0.002 0.014
See also #73,
register_font()
can be expensive becuas: