[Feature Request] "Sticky Option" - a persistent dropdown option, regardless of input

[mikevaux]

I did:

• Search for if my issue has already been submitted
• Make sure I'm reporting something precise that needs to be fixed
• Give my issue a descriptive and concise title
• Create a minimal working example on JsFiddle or Codepen
  (or gave a link to a demo on the Selectize docs)
• Indicate precise steps to reproduce in numbers and the result,
  like below

(This is a feature request rather than a bug so some of the above aren't applicable I don't think...)

It would be great to be able to mark an option as 'sticky' (or similar), which would mean that it always shows up as an option, regardless of the user's input in the text field. The main use case of this, which is a relatively common piece of UI I think, would be for an 'Other' option, whereby the 'Other' option would always show at the bottom of the list.

My specific use case is for bank account providers; we do not support every single provider (there are a lot), so sometimes a user will type their provider into the autocomplete field, but it is not there, so they are left with an empty list of options. In this case, what they'd need to do is select 'Other', but obviously 'Other' has been filtered out along with all the others, so currently the only way they can do this is clear their previous input and know to then find 'Other'.

I did have a look through the documentation (and have been using Selectize for a while) as well as trying a few searches in closed issues but couldn't find anything, but apologies if I've missed something! :-)