fix(sbb-menu): menu action focus on mobile

[dauriamarco]

Sets the focus on the first focusable inside the menu on open (mobile).

[kyubisation]

LGTM 👍

[codecov-commenter]

Codecov Report

Merging #2103 (855cc4b) into master (ab917b0) will decrease coverage by 18.50%.
Report is 1789 commits behind head on master.
The diff coverage is 30.54%.

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@@             Coverage Diff             @@
##           master    #2103       +/-   ##
===========================================
- Coverage   54.85%   36.35%   -18.50%     
===========================================
  Files          49      288      +239     
  Lines        1659    11004     +9345     
  Branches      406     2412     +2006     
===========================================
+ Hits          910     4001     +3091     
- Misses        671     6735     +6064     
- Partials       78      268      +190     

Files	Coverage Δ
...c/components/sbb-action-group/sbb-action-group.tsx	100.00% <100.00%> (ø)
...mponents/sbb-alert-group/sbb-alert-group.events.ts	100.00% <100.00%> (ø)
src/components/sbb-alert/sbb-alert.events.ts	100.00% <100.00%> (ø)
...onents/sbb-autocomplete/sbb-autocomplete.events.ts	100.00% <ø> (ø)
src/components/sbb-card-badge/sbb-card-badge.tsx	100.00% <100.00%> (+11.11%)	⬆️
src/components/sbb-card/sbb-card.stories.tsx	0.00% <ø> (ø)
src/components/sbb-card/sbb-card.tsx	90.00% <ø> (ø)
.../sbb-checkbox-group/sbb-checkbox-group.stories.tsx	0.00% <ø> (ø)
...mponents/sbb-checkbox-group/sbb-checkbox-group.tsx	33.33% <ø> (ø)
src/components/sbb-checkbox/sbb-checkbox.events.ts	0.00% <ø> (ø)
... and 55 more

... and 239 files with indirect coverage changes

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