UI navigation without touch

[l1l17h]

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Pre-Submission checklist

• [x] There is no existing issue that already asks for this feature.
  
• [x] The feature already exists in rclone (on your PC or in Termux)
• [x] I am prepared to help make this feature

What version of RCX are you using (About -> App version)?

1.12.2

What problem are you trying to solve?

Using keyboard or remote it's not possible to select files or folders from the item list

What should RCX be able to do differently to help with this problem?

Generally, navigation to all elements of the UI should be accessible using keyboard or remote without touch or mouse.

[alexanderadam]

This issue surely has some overlappings with #67 since TV devices also don't have any touch navigation.