Small doc updates

[cmdcolin]

• Adds readme's to the vanillsjs demos
• Updates component npm pages with links to demos
• Small updates to @jbrowse/img readme
• Bump docusaurus version

[codecov]

Codecov Report

Merging #2946 (7a294e5) into main (d14ea8e) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2946   +/-   ##
=======================================
  Coverage   60.74%   60.74%           
=======================================
  Files         601      601           
  Lines       27329    27329           
  Branches     6643     6643           
=======================================
+ Hits        16600    16602    +2     
+ Misses      10419    10418    -1     
+ Partials      310      309    -1     

Impacted Files	Coverage Δ
products/jbrowse-web/src/util.ts	27.27% <0.00%> (ø)
...quenceRenderer/components/DivSequenceRendering.tsx	94.68% <0.00%> (+2.12%)	⬆️

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