Add insert bar

[Copoder]

Changes:

Add an InsertBar below the editor. The visibility of the InsertBar can be toggled by the user clicks the T menu button.

InsertBar

The InsertBar enables users to insert basic markdown syntax into the editor.

Currently, it supports the following syntax:

• Bold
• Italic
• Bulleted list
• Numbered list
• Blockquote
• Link
• Image
• Code

Screenshot