Add shortcuts for basic markdown, same as in github edit page

[complynx]

Here, in gh, when you send text, you have preview tab and a bunch of buttons to help you out. Not everyone can get that you can do md formatting in the text

[notmd]

for anyone who want to implement this here is a few packages I found https://github.com/bytedance/bytemd https://github.com/uiwjs/react-md-editor