Mobile devices: Detect and add a warning within the application that it currently does not support touch keyboards

[NathanLovato]

We still have some users trying to follow along the application using a touch keyboard, and they cannot input text in the code editor at the moment.

While we have a warning on the website, we don't have one within the application, and so it's not available on every mirror of the application.

This task is about designing and showing something to the users so they know that they won't be able to do the practices without a physical keyboard.