refactor: add eslint rules

[mlmoravek]

I have added eslint with a set of recommended lint rules, and also fixed some bugs with the applied rules.
These will help improve development and maintain consistent code quality.

Proposed Changes

• Added eslint and rules
• Lint components

Mainly changed files are:

• oruga-next/.eslintrc.cjs (add lint rules)
• oruga-next/package.json (add eslint dependencies)
• docs-next/docgen.config.js (fix docs)

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[codecov]

Codecov Report

Attention: 224 lines in your changes are missing coverage. Please review.

Comparison is base (7db611c) 62.72% compared to head (7efc3c6) 62.34%.

❗ Current head 7efc3c6 differs from pull request most recent head 5958afb. Consider uploading reports for the commit 5958afb to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #604      +/-   ##
===========================================
- Coverage    62.72%   62.34%   -0.38%     
===========================================
  Files           79       79              
  Lines         5529     5617      +88     
  Branches      1526     1576      +50     
===========================================
+ Hits          3468     3502      +34     
- Misses        1950     2004      +54     
  Partials       111      111              

Flag	Coverage Δ
oruga	65.92% <ø> (ø)
oruga-next	47.47% <48.97%> (-0.78%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...ackages/oruga-next/src/utils/BaseComponentMixin.ts	64.70% <ø> (-3.59%)	⬇️
packages/oruga-next/src/utils/CheckRadioMixin.ts	63.63% <ø> (ø)
packages/oruga-next/src/utils/FormElementMixin.ts	41.66% <ø> (-2.78%)	⬇️
packages/oruga-next/src/utils/MatchMediaMixin.ts	63.15% <ø> (ø)
packages/oruga-next/src/utils/config.ts	57.14% <ø> (+2.59%)	⬆️
packages/oruga-next/src/utils/helpers.ts	8.47% <ø> (-0.57%)	⬇️
packages/oruga-next/src/utils/icons.ts	90.90% <ø> (ø)
...es/oruga-next/src/components/collapse/Collapse.vue	89.47% <88.88%> (ø)
...es/oruga-next/src/components/checkbox/Checkbox.vue	73.91% <66.66%> (-2.28%)	⬇️
...ckages/oruga-next/src/components/button/Button.vue	72.50% <76.00%> (+2.22%)	⬆️
... and 5 more

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