Issue title: put chosen values in multi list on the top of the dropdown
 Issue body: use case:
i choose something from very long list
run the script.
now need change, but
i don't know what is chosen in the dropdown
i don't want to reload the rest of the fields because there are a lot of them

another problem:
i FORGET that something is already chosen
and delete something by mistake

thnanks

 Comments: 
 Comment 0: Hi @yosefy, thanks for the proposal, nice idea. I need to rethink how to properly implement it from the UX perspective: to avoid jumping values on the selection and probably keep a default behaviour for short lists.
 Comment 1: i took the idea from past usage of  rundeck
it was very useful from experience
thaks

On Wed, Apr 17, 2019 at 10:55 AM Iaroslav Shepilov <aharper@example.org>
wrote:

> Hi @yosefy <https://github.com/yosefy>, thanks for the proposal, nice
> idea. I need to rethink how to properly implement it from the UX
> perspective: to avoid jumping values on the selection and probably keep a
> default behaviour for short lists.
>
> —
> You are receiving this because you were mentioned.
> Reply to this email directly, view it on GitHub
> <https://github.com/bugy/script-server/issues/208#issuecomment-483978502>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AMVy7TEQvBJt-7GaeUAPIYXNH6Rxx-G2ks5vhtNtgaJpZM4c0anc>
> .
>

 Comment 2: Maybe second answer from here can help? 

https://stackoverflow.com/questions/63299745/how-to-highlight-certain-value-on-select-box-dropdown-first-time-expanding-list
{'source': 'GithubIssues', 'repo_name_with_owner': 'bugy/script-server', 'issue_id': 434140956, 'repo_stars': 977.0}