Add XEP-0393: Message Styling using QTextDocument's markdown support
XEP-0393: Message Styling seems to be more or less like markdown. Implementing this should also fix things like bracket parsing what the issue was initially meant for (see below).
URL not parsed correctly if in brackets () []
An URL is not detected if it's in brackets:
[https://www.kaidan.im/](https://www.kaidan.im/)