Even better markdown handling

[MahdiBM]

Penny makes a lot of effort to show GitHub markdown strings in Discord, in a form that is nicer to see in Discord.
But I still want to make it even better:

• Penny should convert strings like #66 to "Replace the "projectboard" workflow currently present in all repos #66" which is also a link, when sending to Discord.
• Also should count the actual string value of only Text elements when doing String.unicodesPrefix() for markdown documents.
• Turn "TODO lists" (like this list here in this issue) into normal bullet-point list, because Discord doesn't render these lists properly.
• "trailingTextMinLength" should only take effect if the text doesn't fit in the maxVisualLength limit at all.

[gwynne]

You're just lucky SwiftMarkdown is built directly atop cmark-gfm (which is literally GitHub's Markdown flavor). That being said, I don't think the automagic conversion of issue/PR numbers to links etc. thing is all that important; they're very context-dependent and don't always work even on GitHub in places you might think they should. Also no one on Discord generally cares.

[MahdiBM]

I care though 🫣

I know not many people care, but if I were to work on penny with that assumption, I should've stopped a long time ago 😅