Add more markdown

[fksdokf]

Some markdown is already visible, but many other are still missing, this is all i found that is missing:

• ### Header
• Subtext (-#)
• Bullet points (- or *)
• Slash command mention (</Name:ID>)
• Strikethrough text (text)
• Spoilers (||text||)
• Multiple line quote (>>>)
• Nested lists

[iProgramMC]

Worth noting that the multiple line quotes are an editor feature and not a Markdown feature.