Selectbox style with autocompete suggestion

[papalotis]

Is your feature request related to a problem? Please describe.
I want to use a selectbox, but also allow the user to input new inputs. st-tags allows me to do this, however the visual design of the tags does not match my intended use where exactly one selection is possible

Describe the solution you'd like
I'd like to see a selectbox style widget being made available. The main change will be visual, functionally the component can be the same as a tag is currently only with the maxtags argument set to 1

Describe alternatives you've considered
An alternative is to use a selectbox for the autocomplete feature and a checkbox next to it that swaps the selectbox with a text_input widget