add typings for timepicker

[YussufElarif]

Summary

The goal of this PR is to add typings for the timepicker element. Thank you 😄

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @YussufElarif to sign the Salesforce Inc. Contributor License Agreement.

[seratch]

Thank you! LGTM

[codecov]

Codecov Report

Merging #1928 (3cfe499) into main (6d23725) will not change coverage.
The diff coverage is n/a.

❗ Current head 3cfe499 differs from pull request most recent head 330b4fc. Consider uploading reports for the commit 330b4fc to get more accurate results

@@           Coverage Diff           @@
##             main    #1928   +/-   ##
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  Coverage   82.18%   82.18%           
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  Files          18       18           
  Lines        1521     1521           
  Branches      436      436           
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  Hits         1250     1250           
  Misses        175      175           
  Partials       96       96           

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