Aladin#getViewImageBuffer support

[Xen0Xys]

For testing purposes, it il possible to save a PNG ArrayBuffer with the following code :

const save = function(arrayBuffer, filename) {
    const blob = new Blob([arrayBuffer], { type: 'image/png' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = filename;
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    URL.revokeObjectURL(url);
}

[bmatthieu3]

Otherwise it is good to merge :)

[bmatthieu3]

Maybe also I think it would be good to add some jsdoc for Aladin.prototype.getViewDataURL and Aladin.prototype.getViewArrayBuffer.
Even maybe do a new method call Aladin.prototype.getView(dataType) with datatype that can be: 'blob', 'url', 'arrayBuffer'

[Xen0Xys]

Maybe also I think it would be good to add some jsdoc for Aladin.prototype.getViewDataURL and Aladin.prototype.getViewArrayBuffer. Even maybe do a new method call Aladin.prototype.getView(dataType) with datatype that can be: 'blob', 'url', 'arrayBuffer'

Do you mean a function to replace getCanvasArrayBuffer and getCanvasDataURL, or a function that calls these two?