[Improvement] [MOBILE] Editing signature: jump to the signature field if the user clicks on it

[tprudentova]

0.13.2, mail.stg.lin-saas.com, tested on Android

1. Open account settings
2. Go to Identities
3. Click Edit for some identity
4. Don't scroll down, click on the signature field
5. Rn after that user needs to manually scroll down to see the field itself

Suggested behaviour: user jumps down for the signature field and the cursor to be visible on the screen

video5447503988717015327.mp4