wasm: use Array when converting bytes into JsValue

[skystar-p]

In wasm environment, just using Uint8Array to convert &[u8] to JsValue gives wrong result. See:

POST / HTTP/1.1
<snip>
-----------------------------39735077602244728713763853857
Content-Disposition: form-data; name="salt"; filename="blob"
Content-Type: application/octet-stream

253215189732323814792583246113167154161341161821110310981725410248203142105158205
-----------------------------39735077602244728713763853857
Content-Disposition: form-data; name="filename"; filename="blob"
Content-Type: application/octet-stream

14792118571925534386625416214323810571220106184438911212196164
-----------------------------39735077602244728713763853857--

application/octet-stream body is printing weird string, not the binary stream (tested on current master).
This patch will fix above issue.

[seanmonstar]

Thanks!