glab config edit

Describe the feature or problem you'd like to solve

glab config command currently has get and set sub-commands which are enough to make things work but once our configuration supports more keys we might want to support a glab config edit command that opens an editor and validates a hand-edited config before updating.

Propose a Solution

Support a glab config edit command that opens an editor and ensures that a hand-edited config is valid before updating

Additional context