update with latest opencv

[dakom]

I tried with the latest opencv (v4 I think) and your instructions almost all work.

It breaks with this change to embindgen.py:

return re.sub(r"^cv\.[a-zA-Z0-9]*\.|cv\.", "", name).replace(".", "_")

Interestingly when I take that out and keep the original replacement, it seems to compile aruco fine - but no Dictionary class o_O

[dakom]

actually - the current repo fails as-is with python ./platforms/js/build_js.py build_wasm --build_wasm