fix(taginput): selection with autocomplete on non string items

[dauriata]

Fixes #886

Proposed Changes

Changes to addItem function to fix selection with autocomplete and non string items.

Changes to createItem and beforeAdding to be used with any input type, I though it could be left open to the developer to use a transform or validation function for any type while using autocomplete.

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 22.08%. Comparing base (484cfe8) to head (3e2237a).
Report is 50 commits behind head on develop.

Files	Patch %	Lines
...ackages/oruga/src/components/taginput/Taginput.vue	0.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           develop     #889       +/-   ##
============================================
- Coverage    56.71%   22.08%   -34.64%     
============================================
  Files           30      110       +80     
  Lines         1511     5285     +3774     
  Branches       544     1946     +1402     
============================================
+ Hits           857     1167      +310     
- Misses         654     3279     +2625     
- Partials         0      839      +839     

Flag	Coverage Δ
oruga-next	22.08% <0.00%> (-34.64%)	⬇️

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