fix(rules): improvements to rules that should only apply to dom nodes

[benmonro]

What:

Why:

How:

Checklist:

• Documentation
• Tests
• Ready to be merged
  

[codecov]

Codecov Report

Merging #129 (8993b8c) into master (c595f94) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #129   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines          358       382   +24     
  Branches        59        68    +9     
=========================================
+ Hits           358       382   +24     

Impacted Files	Coverage Δ
src/assignment-ast.js	100.00% <100.00%> (ø)
src/createBannedAttributeRule.js	100.00% <100.00%> (ø)
src/rules/prefer-to-have-class.js	100.00% <100.00%> (ø)
src/rules/prefer-to-have-value.js	100.00% <100.00%> (ø)

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[github-actions]

🎉 This PR is included in version 3.6.4 🎉

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• npm package (@latest dist-tag)
• GitHub release

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