WASM support

[mfulton26]

instructions on building with Emscripten or something similar would be great

a package published to npm/GitHub for use in node bundlers (like webpack) would be even greater

[kennyhyun]

I tried to add wasm build and added an example React app.

https://github.com/yushulx/zxing-cpp-emscripten/tree/master/build-wasm
https://github.com/kennyhyun/zxing-cpp-wasm
(master...kennyhyun:zxing-cpp-wasm:kenny/main)

Please have a look if anyone interested...

p.s. Not sure how to make it npm package though

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not sure why I put a wrong url lol

that was what I referenced first