Load custom font file

[ignacioblit]

I have found no way of loading a custom font file using the Watermark method of the library. Is there a way to do this dynamically that I may be missing? (Not preloading the font on the system).

After researching LibVips I found that the vips_text function accepts a fontfile parameter: https://libvips.github.io/libvips/API/current/libvips-create.html#vips-text

Is it be possible to implement this on the Watermark method?