Canvas example needs HTML Canvas element

[misaim]

Where in the docs did you come across this?
https://rustwasm.github.io/docs/wasm-bindgen/examples/2d-canvas.html

Describe what about it does not make sense
Currently this documentation doesn't include a custom html file. This raises a confusing Uncaught (in promise) RuntimeError: unreachable executed error message on loading of the compiled .wasm file.

Note that I'm using --target web (although no-modules has the same problem) - I am unsure if using all the fancy bundle tools generates html with a canvas element by default.

How could we improve it?
Include a html file. Can be as basic as possible, with a dedicated canvas element (id of "canvas") e.g:
<canvas id="canvas" width="150" height="150"></canvas>
...Taken from the hosted example.