x/website/tour: not accessible to screen readers

[Deleplace]

The editable code textbox at go.dev/tour appears as a blank canvas to developers who are blind or visually impaired.

[Deleplace]

This has been true for some time, but I couldn't find an open issue for this so I'm creating one.

[Deleplace]

I tested in Windows with NVDA. All lines and characters are said as "blank"

Go.Tour.nvda.blank.blank.blank_.mov

As a comparison, in the Playground the lines and characters are said correctly

Go.Playground.nvda_.mov

[Deleplace]

This seems to be caused by the use of codemirror5.

A possible fix would be to use codemirror6 or monaco instead.

[Deleplace]

cc @jamalc

[Deleplace]

Sorry for the noise, this is of course a dupe of #1437 in repo golang/tour