feat: allow continuation of expander menu

[DKhalil]

In our case this was needed for a multi-step autofill, where first you select a type to insert, and then do the actual search.

e.g.:

#type:ID

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[keithamus]

Would be great to see some tests and documentation for this feature. I'm struggling a little to figure out what this is supposed to do.

[DKhalil]

@keithamus added some documentation to the README and a few tests. I hope it's clearer now, but to re-iterate:

I want to enable something like this:

#pr:123
#issue:123
#commit:123
#project:1234

Where the first dropdown would show the various data types, following a second one that allows the search for the actual entries.

[DKhalil]

@keithamus Is there anything still left unclear or requiring further expansion?

[keithamus]

This LGTM

[DKhalil]

@keithamus fixed the breaking tests

[keithamus]

Thanks for your perseverance on this one @DKhalil