Add Canonic link to readme

[ollie-dawes]

Hey, bit of a shameless plug but I wanted to let you know that if you add https://www.canonic.com/#https://raw.githubusercontent.com/aaronsnoswell/QMLVirtualJoystick/master/virtual_joystick.qml to your readme then people can see a live preview of the project.

I've been using this project as a test case for the last few months so thought I'd give you a heads up. Also if you have any other qml stuff let me know, I'm putting together a QML website directory and need examples.