[gitk] moving the cursor position in search boxes

[Lyndon Brown <jnqnfe@xxxxxxxxx>]

Hi,

Please can the UX of gitk be improved by allowing left and right keys
to move the cursor position in the search boxes, which is currently
only possible with a mouse click (the left/right keys just do nothing).

I'm a Debian Linux user, running version 1:2.28.0-1. This annoyance has
existed for a long time.