Decide what to do with react-virtualized-select dependency

[valentijnnieman]

The react-virtualized-select package we're using is no longer being updated by its author. There are a few bugs associated with our Dropdown component, https://github.com/orgs/plotly/projects/4#column-3856815 and we are missing out on the updates to react-select that react-virtualized-select is using internally. We have a couple of options:

• Build our own (virtualized) dropdown component
• Fork react-virtualized-select and keep it up to date ourselves (or ask if we can be maintainers - the author mentions he is looking for someone to maintain)

[T4rk1n]

I vote for a custom one, will be better integrated with our props system.

[Marc-Andre-Rivet]

Linking to plotly/dash-table#250