Lint trailing whitespace (#3230)

CONTRIBUTING.md

@@ -5,7 +5,7 @@ For a detailed guide, please see https://esphome.io/guides/contributing.html#con
 Things to note when contributing:
 
  - Please test your changes :)
- - If a new feature is added or an existing user-facing feature is changed, you should also 
+ - If a new feature is added or an existing user-facing feature is changed, you should also
    update the [docs](https://github.com/esphome/esphome-docs). See [contributing to esphome-docs](https://esphome.io/guides/contributing.html#contributing-to-esphomedocs)
    for more information.
  - Please also update the tests in the `tests/` folder. You can do so by just adding a line in one of the YAML files