Add ⚡️ content to `Private key management` > `Automatic cloud backup`

[GBKS]

First step is to review the page for additions and changes.

Ideas:

• Add info about versatility of this solution. It can easily also be used for backing up Lightning channels, etc.

[sbddesign]

I can take this one. There will be some overlap with what I have been working on in the Onboarding > Backups section.

[danielnordh]

Closed by #559