Optimize svg icons, fix JLab 1.1 issue

[jtpio]

This should fix #376.

The voila icons stopped showing in JupyterLab 1.1.

This change optimizes the svg files and sets the width and height to 16 (same as the core icons).

[jtpio]

cc @maartenbreddels @martinRenou

I would like to make a new release of the extension once this gets in.

[vidartf]

Should you keep the old versions? I think they are likely to be better for editing if you want to make changes. Or are the originals somewhere else?

[jtpio]

Thanks @vidartf for double checking.

The icons are a copy of the voila-square.png version from the docs.

By the way, do you know why this started to break in JupyterLab 1.1?

[vidartf]

I believe it might be this PR? jupyterlab/jupyterlab#6034

[jtpio]

Yes

[jtpio]

I think we can merge this one and make a new release.

The icons are still svg, and can be edited again if needed (or from the original square icon). Also the visual identity for voila will most likely change in the future.

[adriendelsalle]

Great @jtpio ! Thank you!

[jtpio]

@adriendelsalle A new version has been published.

To update: jupyter labextension update @jupyter-voila/jupyterlab-preview