iOS 11: Delete Backwards Workaround

[jleandroperez]

Details:

iOS 11's insertText / deleteBackward's inner workings result into loosing the typingAttributes. This fix is analog to the one introduced via #725.

Fixes #749

cc @diegoreymendez
Thanks in advance!

To test:

1. Verify that the unit tests pass
2. Launch Aztec > Empty document
3. Toggle Bold
4. Type Here + Newline
5. Toggle Italics
6. Type Theree + Backspace twice
7. Type e
8. Verify that the new e character is in italics.

[diegoreymendez]

The PR is mostly fine with one exception. Try this:

1. Apply any header style
2. Type something
3. Press ENTER once
4. Type "1"
5. Backspace once.

PROBLEM: The header style is applied to the second line.

To do:

We should add a unit test for this scenario.
We should check if the care is at the beginning of the paragraph:

• If the care is at the beginning of a paragraph, we should only copy regular (non-paragraph) styles.
• If the care is anywhere else, we should copy all styles.

[jleandroperez]

@diegoreymendez nice catch!. The scenario outlined has it's own issue (#747), and it's own PR though (#754). Would you like me to merge that PR in here?

Edited:
This ^^ is actually inaccurate, the scenario outlined by Diego is different. Addressing here!

[diegoreymendez]

This is a golden PR. Nice changes!

[diegoreymendez]

Need this PR in to test the following PR in line. We have several, so I'm overriding Circle for now.

We'll be letting Circle run for the last PR, so that all of the changes are checked.

[jleandroperez]

Thanks for the review Diego!