Ability to customize UITextView that's created in attributedString configuration of MarkdownTextView

[lvnkmn]

Hi there!

It would be really nice if UITextViews created by MarkDownAsAttributedStringViewConfiguration could be further customized just like views created in MarkDownAsViewViewConfiguration can be customized though the public var onDidConvertMarkDownItemToView:((_ markDownItem: MarkDownItem, _ view: UIView) -> Void)? closure.

this way scrolling, contentInsets etc. can be changed as desired.

[lvnkmn]

I'll create a PR for this in a bit.

[Basca]

Released as version 9.2.1: https://github.com/M2Mobi/Marky-Mark/releases/tag/9.2.1

[lvnkmn]

Super. Thanks Bas!