test: use Jest with Snapshots

[nschonni]

Short description of what this resolves:

Just trying this one again to see if the random CI issues have resolved

Proposed changes:

[nschonni]

Interesting. Forcing on the colour may have resolve some of the issues, but now I need to update that SVG test that was created after the orginal coversion

[codecov]

Codecov Report

Merging #823 (e935dcc) into master (a629d0b) will decrease coverage by 31.71%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master     #823       +/-   ##
===========================================
- Coverage   98.58%   66.86%   -31.72%     
===========================================
  Files           1       48       +47     
  Lines         917     3217     +2300     
  Branches      191      360      +169     
===========================================
+ Hits          904     2151     +1247     
- Misses         13     1066     +1053     

Impacted Files	Coverage Δ
src/core/rules/attr-lowercase.ts	100.00% <100.00%> (ø)
dist/htmlhint.js
src/core/rules/attr-no-duplication.ts	100.00% <0.00%> (ø)
src/core/rules/inline-style-disabled.ts	100.00% <0.00%> (ø)
src/core/rules/alt-require.ts	100.00% <0.00%> (ø)
src/core/rules/attr-value-not-empty.ts	100.00% <0.00%> (ø)
src/cli/formatters/compact.ts	0.00% <0.00%> (ø)
src/cli/htmlhint.ts	0.00% <0.00%> (ø)
src/core/rules/attr-no-unnecessary-whitespace.ts	100.00% <0.00%> (ø)
src/core/rules/attr-unsafe-chars.ts	100.00% <0.00%> (ø)
... and 40 more

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