Add WebGL target

[jasonboukheir]

I've been struggling to get WebGL crypto functions to work in my Algorand SDK library. I have been using .jslib native plugins to handle them, but the APIs are not the same as libsodium.

Well I'm pleased to show off that I got source libsodium working in WebGL! Check this out: https://github.com/CareBoo/unity-algorand-sdk/tree/8c1b360d745cfcb1d621d355f56fa959c33a8957/Runtime/Algorand.Unity.Crypto/Plugins/WebGL

I have only tested ChaCha20Poly1305, Ed25519, and Sha512, however, I'm really surprised it worked!

So the steps to copy from the libsodium project were the following:

1. Give each file a unique name.
2. Replace all #includes with the new names.
3. Flatten the folders.
4. Remove all directories from #includes.
5. Set explicit version and minimal in the version.h.in -> version.h file.

I recommend doing something similar to add this to WebGL. It should also just work for any platform using IL2CPP, so it opens this project up to loads of other platforms!