Fix XML entities in generated JavaScript

[jsamr]

Summary

This patch fixes the issue reported in #516. The fix targets @svgr/hast-util-to-babel-ast. The handler for XML text parsing now creates a string literal which content is entity-decoded via the entities package. The reference for XML entities is available here: https://www.w3.org/TR/REC-xml/#sec-internal-ent
To be fully XML compliant, we would also have to substitute external entities, those declared in the body of the document. However this is a substantial endeavor out of scope of this fix.

Test plan

Two tests have been added in hast-util-to-babel-ast test folder. See capture below:

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[codecov]

Codecov Report

Merging #553 (7b8cc96) into main (7e890a9) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #553      +/-   ##
==========================================
+ Coverage   90.89%   90.99%   +0.10%     
==========================================
  Files          31       31              
  Lines        1076     1077       +1     
  Branches      325      323       -2     
==========================================
+ Hits          978      980       +2     
  Misses         92       92              
+ Partials        6        5       -1     

Impacted Files	Coverage Δ
packages/hast-util-to-babel-ast/src/handlers.js	85.41% <100.00%> (+2.43%)	⬆️

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[micheljung]

@gregberge I hope you enjoyed your vacation, and that you can merge and release this fix soon :D

[lex111]

friendly ping for @gregberge, we need this fix :)

[Droppers]

@gregberge, sorry to bother but any ETA when this pull request will be merged and a new version will be published?

Very surprised this little users ran into this problem (or assumed it's SVGO's fault?)

[gregberge]

Sorry for the delay, thanks for this fix!