feat(button): enhance SButtonGroup interface

[NozomuIkuta]

Asana: N/A

This PR is to enhance SButtonGroup component in the following points:

• Add Icon property to ButtonGroupItem interface, which is prioritized than label if both exist
• Add disabled property to ButtonGroupItem interface
• Add beforeText and afterText props to show some computed text (e.g. current page)
• Add click event, which is emitted with value of the clicked button, so that beforeText and/or afterText can be calculated on the fly
• Modernize some lines of code (e.g. defineProps with TypeScript)
• Fix some styles (e.g. overflown inner height)

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[codecov]

Codecov Report

Base: 76.37% // Head: 76.02% // Decreases project coverage by -0.36% ⚠️

Coverage data is based on head (5f957d7) compared to base (27223ff).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #222      +/-   ##
==========================================
- Coverage   76.37%   76.02%   -0.36%     
==========================================
  Files         106      106              
  Lines        8911     8780     -131     
  Branches      436      432       -4     
==========================================
- Hits         6806     6675     -131     
  Misses       2105     2105              

Impacted Files	Coverage Δ
lib/components/SButton.vue	100.00% <100.00%> (ø)
lib/components/SButtonGroup.vue	100.00% <100.00%> (ø)

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[kiaking]

We've discussed this internally and made changes accordingly.