[iOS]: Fix issue where heading blocks are not behaving properly.

[etoledom]

Fixes wordpress-mobile/gutenberg-mobile#355

This PR forces the typing attributes to be corresponding with the Heading level, when Aztec is used to display Heading blocks.

With @diegoreymendez we looked into the possibility of fixing this on the Aztec level but it easily became super complicated. So we decided for an RNAztecView approach.

The BlockFormatHandler and BlockModel are meant to be easily extensible, in case we need similar implementations with other blocks in the future.

Refertences:

mobile-gutenberg branch: issue/ios-heading-behavior
gutenberg PR: WordPress/gutenberg#12869
Aztec-iOS PR wordpress-mobile/AztecEditor-iOS#1108

To Test:

Setup:

• Checkout gutenberg-mobile branch issue/ios-heading-behavior.
• Run git submodule update to checkout submodules commits.
• Run yarn preios to force update the Aztec version.
• Run yarn start:reset
• Open the iOS example project on Xcode open ios/gutenberg.xcodeproj.
• Clean build folder.
• Build and run (from Xcode or from yarn ios)

Testing:

• Create a Heading block.
• Check that the heading block style is the correct.
• Type and delete text, change Heading levels, etc...
• Check that everything looks fine.
• Format a word of the title with Italic and change Heading levels.
• Make sure that the Italic format is not removed.
  • Bold has an issue but is already solved on master.

Thank you!

[etoledom]

Sent a couple of commits to solve some issues found by @koke .
I also updated the To test description with an extra setup step and extra details to test.

[diegoreymendez]

I could completely remove the header style by selecting all text and deleting everything. You mentioned in this PR it's a partial fix though so if that's known, everything else looks fine to me.

I also added a comment related to the documentation of a protocol.

[diegoreymendez]

I think it'd be a good idea to document this new protocol to define what its scope is (what does it take care of specifically? what's it purpose?).

This is kinda minor but it's good in making sure all devs stay synchronized moving forward.

[etoledom]

Thanks for your review @diegoreymendez

That odd behavior should not be present. At some point it was solved but seems to be there again.
I pushed a commit trying another way to solve the p tags issue, hopefully that helps.

[diegoreymendez]

Works as advertised.