Create a markdown shortcuts plugin

[umaranis]

Implement a markdown plugin to support the following:

• Type # to create a heading. Supports H1 to H6 (e.g. ### creates H3)
• Type > to create a quote
• Tyoe - to create an unordered list
• Type [] to create an check list
• Type 1. to create an ordered list (you can use any digit instead of 1 as starting number)
• Enclose text in backticks to convert it to inline code (e.g. `let value = 5`)
• Enclose text in * to make it italic (e.g. *italic text*)
• Enclose text in _ to make it italic (e.g. _italic text_)
• Enclose text in ** to make it to bold (e.g. **bold text**)
• Enclose text in __ to make it to bold (e.g. __bold text__)
• Enclose text in *** to make it to bold and italic (e.g. ***bold text***)
• Enclose text in __ to make it to bold and italic (e.g. ___bold text___)
• Enclose text in ~~ for strikethrough (e.g. ~~strikethrough~~)
• Create a link using []() e.g. [Syed Umar Anis](http://umaranis.com)
• Create a image using ![]() e.g. 
• Create horizontal rule using one of the following: --- , ___ , ***