Documented the characters that provoke a YAML escaping string

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | all
| Fixed tickets | #4197
Yeah, I really understand that. I read some parts of the specs when fixing some issues in the component. But I'm really far from understanding them in depth though.

Hopefully, @stof can have a look at this pull request and provide some feedback. Please. :)