Added SVG Pane

[philippjfr]

Adds an SVG pane, unlike other image types the size and/or aspect ratio of the SVG cannot be easily computed ahead of time, but it still seems default to its native size unless explicitly overridden.

[codecov-io]

Codecov Report

Merging #85 into master will increase coverage by 0.06%.
The diff coverage is 97.56%.

@@            Coverage Diff             @@
##           master      #85      +/-   ##
==========================================
+ Coverage   91.48%   91.55%   +0.06%     
==========================================
  Files          23       23              
  Lines        3537     3577      +40     
==========================================
+ Hits         3236     3275      +39     
- Misses        301      302       +1

Impacted Files	Coverage Δ
panel/tests/test_panes.py	98.52% <100%> (+0.11%)	⬆️
panel/pane.py	80.82% <95%> (+0.82%)	⬆️

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[jbednar]

Have you tested networkx, which generates graphviz objects that have _repr_svg_?

[philippjfr]

I tested shapely which has a _repr_svg_, don't think networkx will be any different.

[jbednar]

Graphviz objects work, but they don't seem to default to their native width as promised:

[philippjfr]

Not sure there is anything we can do about it tbh, there is simply no reliable way to determine the size or aspect ratio of the svg ahead of time.

[jbednar]

Not sure what you mean by "ahead of time"; the SVG is static once the Pane is instantiated in this case, right?

[philippjfr]

By ahead of time I mean before it is rendered into the browser's DOM.

[jbednar]

Ah. There might be some Python libraries that could at least return the aspect ratio without rendering it, and probably a bounding box, though of course the browser might not respect that. But not something to work on now...