Migrate stylelint

[Crashillo]

Closes #2563

✌️ What does this PR do?

Removes sass-lint deprecated library, in favour of stylelint

• HoundCI config updated
• NPM scripts updated

Considerations

The following rules have been disabled. Perhaps we should satisfy them in a future.

• at-rule-no-unknown: null
• no-descending-specificity: null
• selector-type-no-unknown: null

[codecov]

Codecov Report

Merging #3592 (42d5f98) into master (8104661) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3592   +/-   ##
=======================================
  Coverage   84.35%   84.36%           
=======================================
  Files         791      791           
  Lines       21147    21147           
=======================================
+ Hits        17839    17841    +2     
+ Misses       3308     3306    -2     

Impacted Files	Coverage Δ
app/models/gobierto_budgets/data/lines.rb	94.28% <0.00%> (+0.95%)	⬆️
app/helpers/gobierto_budgets/application_helper.rb	64.58% <0.00%> (+1.04%)	⬆️

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[jorgeatgu]

We can add our own file of stylelint rules, including comments in the rules to give context to the errors.

Example

[Crashillo]

Hahahaha, funny error messages