Add table and plot download button for csv, png, svg, html

[joehart2001]

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Summary

Created a better way of doing table downloads which uses less code + added plot downlaods

TODO: (maybe in another PR) asset downlaods e.g. phonon dispersions, diatomics etc and maybe structure downlaods?

Linked issue

Resolves #218

Testing

[ElliottKasoar]

This works really well!

So does this only make it possible to download tables, and not the plots etc? Is there a way we could extend it to the full set of test/category outputs?

[joehart2001]

@ElliottKasoar opinions on structure downloads? we can do images but maybe even xyz files too. could be cool but can come under the asset download PR

[ElliottKasoar]

@ElliottKasoar opinions on structure downloads? we can do images but maybe even xyz files too. could be cool but can come under the asset download PR

WEAS should have some sort of download option: superstar54/weas-widget#13 / https://weas-widget.readthedocs.io/en/latest/gui.html#buttons

We may just need to enable the GUI?

Then I agree being able to download the file itself would be nice.