Add hint to cycle through color themes

[thearyanahmed]

It could be obvious for some. But I spent some time to figure out. Hoping this PR would help others save a few seconds.

[zerebos]

I actually don't understand this hint myself. What are you using the arrow keys to do?

[thearyanahmed]

😅
On the colors page, there is a list of colors (color schemes). We can use left and right arrow keys to cycle through the list of color schemes. So everytime, we don't need to manually click the dropdown list and select one.

[adamalston]

We can use left and right arrow keys to cycle through the list of color schemes.

What browser and OS are you using? I can't traverse the list of options using the left and right arrow keys in Edge on macOS. I have to select the select and then click the option I want to select.

Also curious to hear if you can traverse the list of options in the select in https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_select.