Allow user to add custom DEFAULT_START_CODEPOINT as in config

[maheit]

As of now we are building fonts from default start code point. But sometime we need to build multiple icons from different svg group. So it was conflict because all its start from same start code point when I run script independently.

So can we allow user to change this from config.

[RomanSkrypnik]

Any updates?
I need this thing to use icons separately from nuxt module