filter conversation use by content (not just title)

[rxgrant]

As a user, when I type in interactive jp c use prompt to narrow conversations, I want some CLI option, interactive keystroke, or prefix sigil to indicate that the contents of the conversation should be searched, not just the titles.

[JeanMertz]

Unfortunately the current prompting library we use does not support filtering on anything not shown in the list. However, I did already build a --grep option which allows you to filter on conversation content before we show the list to show in jp c use.

See: #679

It's not 100% what you requested, but it works well enough. We can still investigate improving the prompting library to support filtering on "non-visible columns", but that is a bigger task.