Problem

Hard to navigate groups via keyboard because long tab selection sequence and no key binding to focus on groups.

Solution

Change tab selection order in a common way (e.g., windows explorer or mozilla thunderbird)

### Tasks
- [ ] When entry table is focused press `shift` + `tab` to focus on groups
- [ ] When groups are focused press `tab` to focus on entry table

Context

https://discourse.jabref.org/t/key-binding-to-focus-groups-interface/3803