Navigation mode: fix tabbing to title

[ellatrix]

Description

Currently in navigation mode, reverse tabbing from the first block does not work correctly. It's supposed to focus the title, but right now it focusses the block appender, then the block wrapper, and then the title. Instead, we focus look at the tabbable element before the block (title element).

How has this been tested?

In navigation mode, pressing Shift+Tab from the first block should focus the title.

Screenshots

Types of changes

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR. .