added support for loading .off files: works but the simplification algorithm seems to break "real-world" objects from ModelNet40 with non-uniform triangle density, e.g. in chair_0451 the overall chair shape disappears, keeping only the seat and its nearby parts connecting it to (now non-existent) legs, so that it looks more like a table; when "simplifying less" (targeting more faces/triangles than 1024, about 7000), the backrest is there but legs are partially missing

Misc. typos

Found via `codespell -q 3 -L uint,lod,iff,pevent`

interpolate texcoords

CMD line version by Chris Rorden added