Show additional properties of options

[mart-w]

When searching for options to configure a service I was setting up, I stumbled upon an option which, at eval time, turned out to be marked as read-only. This was not clear from the search results and I would’ve skipped that option in my config if I had known this beforehand.

As a user of the options search, I would love if properties like that showed up in the detail view of the individual search results so that I know whether the entry is relevant to me or not. It might also be worth looking through the other keys of lib.mkOption in case there are other things worth displaying, too. For example, the relatedPackages property sounds like a handy thing to know about it if it set.