Convert web encoding to utf8

[Dall127]

Update web implementation to use UTF-8 for encoding, and updating unit tests

[simolus3]

Could you explain the need for these changes a bit more? The intention here is to store a Uint8List as a string because that's the interface the underlyng web API is giving us. Obviously, the string shouldn't be much larger than the original byte array. So a byte value x should be represented by the char code x as well. This is exactly what latin1 is doing. Note that the byte data we want to store is not always a string, this needs to work for all byte sequences, including those that aren't valid utf8.

[Dall127]

That's a valid point; In full honesty, I just barely tested out the purpose on my live site and it didn't actually fix the issue, so I apologize for jumping the gun on making a merge request. I'll make an issue here in a moment describing the actual problem I'm trying to solve.