Fixes #1895 Changed most `println` to `info` in examples, some to `warn` when it was useful to differentiate from other more noisy logs. Added doc on `LogPlugin`, how to configure it, and why (and how) you may need to disable it
This PR adds a small example that shows how to use Keyboard modifiers, as shown in [this](https://github.com/bevyengine/bevy/issues/1654#issuecomment-798966921) snippet. Fixes #1656. Co-authored-by: guimcaballero <guim.caballero@gmail.com>