Add emoji support

[s77rt]

:wave: => 👋

• Requires MD4C extension

[s77rt]

On iOS this may be challenging

NSTextContentStorageDelegate textContentStorage:textParagraphWithRange:

When non-nil, textContentStorage uses the text paragraph instead of creating the standard NSTextParagraph with the attributed substring in range. The attributed string for a custom text paragraph must have a length of range.length.