option to switch driving to correct side of road

[benknowles]

No description provided.

[lrvl]

Thanks!

[ppearson]

It was already "correct" for people in some countries, including the author by the looks of their domain name :)

[tteskac]

@benknowles few points:

• I would suggest to adapt this PR so that your mirror CSS style is toggled with a button press, e.g. "S" (for "side") or whatever, because of what @ppearson said.
• Just a kindly suggestion in general: use meaningful commit messages instead of "Updated index.html".

[jes]

I'm fine in principle with an option to swap the lane, but note:

• the very subtle aeroplane effect will have the lights in the wrong colours if you do this (maybe you don't care)
• I still want the default to be driving on the left

Possibly if we make the popup panel suggested in #1 (like in https://rezmason.github.io/drivey/ ) then that would be a good place to put the button to swap the lanes.