Issue Overview

When entering some text in a block and moving to the next block, I want to be able to quickly return to the previous block to change my typo or revise my content.

Steps to Reproduce (for bugs)

1. Create a fresh post
2. Enter some stuff in the title block
3. Tab to the next block (text)
4. Notice your typo
5. Shift-tab back to the title block, in 14 steps.

Expected Behavior

I expect to more easily return to the block I came from.

Possible Solution

It would be acceptable to have either a short-key to jump to the previous block or have a navigational choice about going to the 'toolbar', 'block-controls' or 'previous block'.