[BetterMarkdown] Full code block, syntax highlighting and font

[WitherredAway]

It would be neat if, when you're doing a "full" code block (with 3 backticks), it codeblocks the text input box entirely until the end like this (ofc it would be accurate to the colour and shape that actually show when the message is sent unlike my scuffed edit)

Secondly, i think syntax highlighting within full code blocks would be sweet, would really add the cherry on top if it's possible :]

Thirdly, it would be very neat if it was possible to make the font within code blocks monospace or whatever font discord uses, when the message is sent