There is built-in functionality to surface a help string to users editing when clauses in keybindings.json as well as extension authors editing when clauses in package.json. We currently don't provide any help in those cases for Positron notebook related context keys.

Acceptance criteria:

1. Positron notebook context key autocompletions include descriptions in keybindings.json
2. Positron notebook context key autocompletions include descriptions in package.json