Update the styling information on the website

I have worked with noUiSlider in the past before, and now I wanted to use it for another project and I’ve realized, the styling works differently and that for example the noUi-background class was gone.

I looked into the release note and found this

• Removed: .noUi-stacking class. Handles now stack themselves;
• Removed: .noUi-handle-lower and .noUi-handle-upper classes;
• Removed: .noUi-background. This is now default;
• Removed: connect: ‘lower’ and connect: ‘upper’. These settings are replaced by connect: [true, false];

But the website still mentions those classes

This should probably be updated to match the new way of styling noUiSlider (I ended up changing the background through .noUi-ltr.

[leongersen]

.noUi-target is now the base element for the slider, and has the background. I didn’t want to add .noUi-background to .noUi-target to prevent hard to debug changes when migrating from a previous version.

[leongersen]

I’ve updated the documentation.