Load files from web links

[habbes]

Besides loading files from the local computer, the file library should ideally also support urls (e.g. images from the web).

[habbes]

PR #42 provides a way to load images from links via the API: xaval.io.files.addImage(url: string, filename?: string).
So this is partially resolve. The missing part is allowing the user to do this via the UI.

[habbes]

Well despite addImage allowing the user to add images from the web, I still get the following error when trying to display such images in the viewer:

Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The canvas has been tainted by cross-origin data.

So it appears there are security restrictions when displaying cross-origin images in the canvas and using getImageData.

I'll look more into this and potential solutions/workarounds when I get there.