Feature summary (what you would like to be able to do and where):
On Wikipedia all code editors providing sytax highlighting also provide a button at the panel above the editor to disable it. There should be such a button on Wikifunctions whenever a textarea with syntaxhighlighted code is exposed

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
On mobile (I am using Firefox for Android with desktop view, but it should apply more broadly) when syntax highlighting is enabled it is very frustrating next to impossible to work with the text area contents. It might be impossible to select stuff, keyboard might not come up, etc. On Wikipedia (and other projects) I would disable syntax highlighting to do something I need, and then perhaps enable it back right away to read code better. It is currently impossible to do this on Wikifunctions.

Benefits (why should this be implemented?):
Most people at least occasionally try to do something on mobile, I suspect there might also be usecases when people need to disable it on desktop.