Add example demonstrating how to correctly decode a stream of characters from winit

> I am still sort of baffled by the myriad of ways of getting a character from a winit key event, so I hope I'm doing this correctly.

I would *love* to see an example for this, but it probably shouldn't be this PR.

_Originally posted by @alice-i-cecile in https://github.com/bevyengine/bevy/issues/11400#issuecomment-1898768973_

Start by locating Bevy's existing input and winit-related examples, since the issue names no file or test. Review how character events are currently exposed, then define the example's expected decoding behavior and verify it by running the relevant example.

Written by the indexing model from the issue text.