Hi!

Thanks for this great library!

As I'm currently testing it out, I have a question on how to avoid creating separate hb_font_t instances.
In my case, I already have unique instances of each font, and depending on the different scenarios, I want to use different font collections.
But, they may well use the same original hb_font_t

The current api only supports skb_font_collection_add_font_from_data() which creates an extra instance of the font, with new cache tables etc. I need to minimize such overhead (every bit counts)

Would it make sense to add a skb_font_collection_add_hb_font() to the api?