Replace Blob::array_buffer with FileReader

[tkubicz]

This PR replaces the Blob:array_buffer usage with the FileReader. This change fixes #470.

This is my first PR to seed, and the first time that I had anything to do with wasm_bindgen so I would really appreciate a review.

[MartinKavik]

Thanks for the PR!

I was looking at it and it looks good, I would add only a few comments.
However I found this code that directed me to function read_as_bytes. Seed's WebSocket wrapper already uses gloo_file::Blob so I can naively imagine that we can just write read_as_byte(&blog).await and done - but I don't know if there are some methods that don't work on Safari, you have better knowledge about it than me now => in that case we would return back to your implementation.

Also we should add unit test or perhaps ideally extend WebSocket example in the Seed repo to use also methodbytes - would you like to do it? I think you are more experienced than me with byte WebSocket messages so I would be glad.

[MartinKavik]

Note: The latest wasm-bindgen supports Blob.stream (see README), but it isn't supported by all browsers, too.

[tkubicz]

HI Martin,

You were right, using read_as_bytes from gloo is much better approach and works just fine on every browser tested by me (Chrome, Firefox, Safari and Opera). I have also extended the web socket example to show the usage of binary messaging.

I'm having trouble with implementing tests for this function, because I have no idea how to convert js_sys::Uint8Array to JsValue and create a blob directly in rust.

[MartinKavik]

Nice, thanks! I'll check how it works on Windows and try to do some quick review.

I have no idea how to convert js_sys::Uint8Array to JsValue and create a blob directly in rust.

Does AsRef<JsValue> for Uint8Array or From<Uint8Array> for JsValue help?
gloo_file has Blob::new and Blob::new_with_option. I assume that gloo's File and native blobs and files has similar methods. Also there are From implementation for casting among all types.

[MartinKavik]

Code looks good, works good :) I've added some short comments. And please update CHANGELOG.md.

[MartinKavik]

Typo

[tkubicz]

Ok, I've corrected the typo, added changelog entry and unit test to check if obtaining bytes really work.