[RNMobile] iOS Image block caption multiline fix

[etoledom]

This PR fixes an issue on iOS where pressing Enter on a Image Block's caption field, it won't do anything.

It should append a <br> tag and create a new line.

gutenberg-mobile side PR: wordpress-mobile/gutenberg-mobile#1107

To test:

• Run the example project.
• Select the Image block with content.
• Write something in the caption field.
• Press enter,
• Check that a new line is created.
• Switch to HTML mode.
• Check that the new line was created by appending a <br> tag.

[SergioEstevao]

Press enter,

or press Shift+Enter ?

[etoledom]

or press Shift+Enter ?

A single Enter should make a new line on the Image Caption field by appending a br tag. That's how web works.

[SergioEstevao]

Working great! Good catch!

[etoledom]

Thank you!