[Feature] Allow Dropdown to Remain Open for multi==True

[TillerBurr]

Closes #2820 (and #2669, an earlier report of the same issue). This PR adds the ability to set the prop close_on_select. If multi is True and this prop is False, the menu selection remains open. If this new prop is True, it is the same behavior. The close_on_select prop has no effect when multi is False, it well essentially ignore the value. I did it that way, as I don't see the value changing after the component is created, similar to multi.

This PR will probably have a need to update the dash docs for the dropdown.

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • Add the prop close_on_select to the dropdown component
  • Add tests
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community

[TillerBurr]

On second thought, it would make more sense to not write over the close_on_select prop. If someone were to change multi, the prop would be lost and it would always close.

[T4rk1n]

On second thought, it would make more sense to not write over the close_on_select prop. If someone were to change multi, the prop would be lost and it would always close.

👍

[WWakker]

@T4rk1n I’m willing to help out for this request. Is there something that still needs to be done? Probably the docs need to be updated for the new parameter but this doesn’t seem to be open source

[T4rk1n]

@WWakker Just need to change this: closeOnSelect={multi ? close_on_select : true} for something that is more user friendly. Either we can set the close_on_select default prop to true or invert the prop condition name to something like stay_open and give closeOnSelect(!stay_open}. I think the first option is closer to the wrapped dropdown api so might be better.