Add ID and class styling selectors

[ImJimmi]

• Apply styles to elements with a specific "id" property.
• Apply styles to elements that include a certain name in their "class" property.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.09% 🎉

Comparison is base (d0fdcb8) 92.48% compared to head (62b3f78) 92.58%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #111      +/-   ##
==========================================
+ Coverage   92.48%   92.58%   +0.09%     
==========================================
  Files         100      100              
  Lines        9689     9752      +63     
==========================================
+ Hits         8961     9029      +68     
+ Misses        728      723       -5     

Files Changed	Coverage Δ
.../variant-converters/jive_MiscVariantConverters.cpp	58.27% <100.00%> (ø)
jive_style_sheets/style-sheets/jive_StyleSheet.cpp	94.18% <100.00%> (+2.42%)	⬆️

... and 1 file with indirect coverage changes

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