Design and implementation of right-to-left or left-to-right for web applications

To me it seems to be a rare sight, but I did notice that on the Material UI framework website there is a toggle/button to switch between left-to-right and right-to-left orientation of user interface elements as seen in the image below:

And the other orientation:

A lot has been said about internationalisation and how to cater for different locales and languages, but it doesn't appear to be a very common requirement for most websites. The Material UI website is an interesting example because it is normally for designers and developers rather than for a general audience.

Are there other examples of this feature made available that are specific to a smaller set of users, or preferably examples that apply to a wider audience group?