[APP-18] Enhance the comment section

[tszhong0411]

We can enhance the comment section by adding more features.

• [X] Support inline code, code block, image, link
• [X] Support Markdown / GFM
• [X] Close reply editor by pressing the Escape key
• [X] ⌘ + Enter to post comments / replies
• [X] Infinite scrolling to fetch the rest of the comments
• [X] Newest / Oldest comments filter

_{From SyncLinear.com | APP-18}