Decode is not unicode aware

[kaol]

See this example program: https://github.com/kaol/servant-jsaddle-bug1

The unicode snowman will be turned into 0x03 instead of ☃ as expected. This will fail with a decode error. The UTF-16 representation of a snowman is 0x2603 which apparently gets truncated to only the least significant byte. For reference, the UTF-8 would encoding is 0xE2 0x98 0x83.

I tried to follow this bug to find out where it originates and seems like https://github.com/ghcjs/jsaddle-dom is a possible culprit. Specifically how fromJSString is implemented in it.

[kaol]

I searched a bit and found ghcjs/jsaddle#144

Seems like the same issue.

[igor-primo]

You may have solved it by now, but there is a pull request that I think solves it, #4