List of webpage improvements

[NunoSempere]

List of webpage improvements for Squiggle:

• Too thin lognormal distributions (Thin lognormal distributions #55)
• Support a cache (GenericOperation: Support Cache for recalculations #172), probably hard
• Improve probability visualizations (Plot probability mass (heatmap), not percentiles #4)
• Allow server side rendering (Allow server side rendering #462; see also a7db7c2)
• Weird rendering bug (some charts don't render correctly on load (but then render correctly when you perturb them) #506)
• CSS error (Playground in Website has height issue: the results go into the footer. #660)
• Add a debouncer (see: tweak: Add debouncing for squiggle editor/playground #664 for a previous attempt)

Of these, I think that:

• CSS error
• Thin lognormal
• Debouncer

might be good places to start.