feat(timepicker): add custom placeholder (#3544)

[fhuschle]

PR Checklist

closes #3544

Before creating new PR, please take a look at checklist below to make sure that you've done everything that needs to be done before we can merge it.

• read and followed the CONTRIBUTING.md guide.
• built and tested the changes locally.
• added/updated tests.
• added/updated API documentation.
• added/updated demos.

[codecov]

Codecov Report

Merging #5429 into development will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           development    #5429   +/-   ##
============================================
  Coverage        52.52%   52.52%           
============================================
  Files                3        3           
  Lines               99       99           
  Branches            17       17           
============================================
  Hits                52       52           
  Misses              37       37           
  Partials            10       10

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[daniloff200]

Tested that locally, LGTM

[daniloff200]

hey @fhuschle !
Thanks again for the PR!
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