Is your feature request related to a problem? Please describe.
When showing a completion list, sometimes instead of finding a specific item, the user wants to browse available options and read their description. For example when using LSP-json and browsing through a list of available options for a given configuration option. In that case, it's annoying to have to press F12 for every completion separately.

Describe the solution you'd like
I propose to introduce a behavior where if the user presses F12 for one item then switching selection to another item will automatically trigger documentation resolve. The flag will be reset on completing or closing the popup.

Describe alternatives you've considered
Pressing F12 for each item.