Implement code and pre blocks support on iOS

[maksg]

Details

Adds support for displaying and customising code and pre blocks on iOS.

[tomekzaw]

Still discussing the expected behavior for codeblocks here

[tomekzaw]

It looks like padding in markdownStyle only affects the size of the rectangle in the background and not the text itself:

It's okay for the initial implementation but ultimately we'd like padding to affect the text layout here as well.

I don't think it's possible to achieve padding for inline code on iOS (Slack for iOS also does not support it).

However, I think it should be possible to implement padding for codeblocks. As for horizontal padding, I've copied this code from blockquotes and it seems to work:

react-native-live-markdown/ios/RCTMarkdownUtils.mm

Lines 119 to 122 in cd42c45

	NSMutableParagraphStyle *paragraphStyle = [NSMutableParagraphStyle new];
	paragraphStyle.firstLineHeadIndent = indent;
	paragraphStyle.headIndent = indent;
	[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:range];

As for vertical padding, ChatGPT says that the only option is to set lineSpacing but this affects the height of the cursor so I'm not really sure how to implement it.

We can implement that in a follow-up PR.

[tomekzaw]

There seems to be some problem with codeblocks containing only one character:

Screen.Recording.2024-04-17.at.01.52.15.mov