Highlight Event Form active day
Again looking at the finished product, when we click a day and get the event form opening,
you'll see that the day that we've clicked on has like a pink background, again just
a bit of a ui sort of thing there to make sure that the user is clear about what day
they've clicked on.
The way we achieved that as I'm sure you can probably guess by now is by adding a class
to that day, and if we look here in the inspector DOM, you'll see there is this class active on it.