Release v0.86.3: New Markdown Parser

• Migrates to the new, faster Markdown Parser
• Adds Note previews on Markdown
• Adds Custom hashtag icons to Markdown
• Adds URL preview boxes to Markdown
• Fixes Missing notifications
• Fixes clickable route not showing the user's npub before loading their name
• Fixes max width of hidden notes making them off-centered
• Moves parsing and saving an embed event to the IO thread
• Improves the secondary button design of the encrypted nsec backup page