Enable Preformatted block in Gutenberg.

[SergioEstevao]

Enables the preformatted block in iOS for release 1.17.0

To test:

• Start a post using Gutenberg
• Add a preformatted block to the post
• See if it works correctly and interacts correctly with other blocks.

Update release notes:

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[koke]

See if it works correctly and interacts correctly with other blocks

Everything else looked good, but I spotted an ugly bug. If you press backspace at the start of a paragraph block after preformatted, when they merge all the newlines in the preformatted block are gone:

[SergioEstevao]

We detected this before in testing and decided to move forward anyway because it's happening on the web version too. Here is the ticket in Gutenberg: WordPress/gutenberg#18476

[koke]

OK, the integration works well, so let's merge this one and handle the bug separately

[peril-wordpress-mobile]

	Fails
🚫	Danger failed to run /app/danger-0.aj3bcejhqx5.ts.

Error TypeError

Cannot read property 'modified_files' of undefined
TypeError: Cannot read property 'modified_files' of undefined
    at Object.exports.default (/app/danger-0.aj3bcejhqx5.ts:22:48)
    at process._tickCallback (internal/process/next_tick.js:68:7)

Dangerfile

17|         const nonGutenbergMatches = matches.filter(m => !m.includes("gutenberg"));
18|         if (nonGutenbergMatches.length > 0) {
19|             fail("Podfile: reference to a commit hash");
20|         }
21|     }
--------------------------------------------------^
22| 
23|     // If changes were made to the release notes, there must also be changes to the AppStoreStrings file.
24|     const hasModifiedReleaseNotes = danger.git.modified_files.some(f => f.endsWith("Resources/release_notes.txt"));
25|     const hasModifiedAppStoreStrings = danger.git.modified_files.some(f => f.includes("Resources/AppStoreStrings.po"));

Generated by 🚫 dangerJS