Add setting to color by query score per alignment for dotplot, support HTML in config slot descriptions

[cmdcolin]

Inspired by https://github.com/tpoorten/dotPlotly/blob/master/example/README.md

Draft PR because maybe a more flexible color system is needed but this is a cool way where we can get a sense strong vs weak homology, useful for looking at ancient whole genome duplication or similar phenomena

may also be useful to have a legend or similar, and add to regular synteny view

[codecov]

Codecov Report

Merging #2483 (751d498) into main (60c79d7) will decrease coverage by 0.09%.
The diff coverage is 33.84%.

@@            Coverage Diff             @@
##             main    #2483      +/-   ##
==========================================
- Coverage   60.93%   60.83%   -0.10%     
==========================================
  Files         590      590              
  Lines       26729    26771      +42     
  Branches     6475     6483       +8     
==========================================
+ Hits        16286    16287       +1     
- Misses      10136    10177      +41     
  Partials      307      307              

Impacted Files	Coverage Δ
.../comparative-adapters/src/PAFAdapter/PAFAdapter.ts	64.28% <15.21%> (-28.90%)	⬇️
...otplot-view/src/DotplotRenderer/DotplotRenderer.ts	61.41% <50.00%> (+0.61%)	⬆️
...pes/renderers/ComparativeServerSideRendererType.ts	64.51% <83.33%> (-1.11%)	⬇️
...ConfigurationEditorWidget/components/CodeEditor.js	100.00% <100.00%> (ø)
...ConfigurationEditorWidget/components/SlotEditor.js	64.28% <100.00%> (+1.12%)	⬆️
.../linear-genome-view/src/LinearGenomeView/index.tsx	84.93% <0.00%> (-0.35%)	⬇️
products/jbrowse-web/src/util.ts	27.27% <0.00%> (ø)

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[cmdcolin]

Added an option for this to the colorBy option for dotplot renderer. Cites the dotPlotly tool since it is inspired by their result (example https://raw.githubusercontent.com/tpoorten/dotPlotly/master/example/Brapa_Bnapus.minimap2.plot.png)

Example rendering with this setting turned on, showing the HTML <ul> and <li> elements in the colorBy description

[cmdcolin]

This should be ready to go

One interesting thing is that I explicitly check if a config slot is a callback using config.isCallback. Is this a stable API to rely on? By checking if it is a callback, I can get the color with a single readConfObject instead of repeatedly calling readConfObject for each dot in a dotplot

[cmdcolin]

The other interesting thing as mentioned above is it now allows HTML in config slot descriptions, and uses our html sanitizer to render it

[cmdcolin]

this should be good to go, I moved the calculation for the mean query score per alignment to only happen if we are actually performing the colorBy:meanQueryIdentity which means if it happens to be slow, it would only happen during this color by setting