Allow to get metrics for variable fonts

[floratmin]

When using a variable font the variation axes have first to be fixed to get the right font metrics. I use for this the package subset-font, which gives back a node buffer, which I can convert to a blob. But unpack fromBlob uses the package blob-to-buffer, which throws when run in node and even converts the blob back to a buffer. So it would be useful to provide a function fromBuffer.

[michaeltaranto]

Hey this is really interesting!

As you've gathered variable fonts are not currently supported, but interesting technique being used here. Im keen to dig into subset-font a little more actually, looks like a potentially avenue to first class what you're doing — but that is a future feature.

Let me have a look at what blob-to-buffer is giving us, as there may be an newer way to handle this. Did you have a repro repo i can test on?