Canvas "fallback" should not be used in tutorials for the purpose of browser support

[robli]

https://www.tpgi.com/html5-canvas-sub-dom/:

Quote

[...] content inside the canvas element is available at all times to assistive technology users and keyboard users can operate links and controls and they are included in the default tab order. So please provide alternatives to on screen canvas content and interactivity in the canvas sub DOM. DO NOT include an asinine message telling the user that they need to get a browser that supports canvas!

Text such as "Your browser does not support the HTML canvas tag" should NOT be used in `<canvas>`, as is the case in https://www.w3schools.com/html/tryit.asp?filename=tryhtml5_canvas_empty.