Include documentation on how to reset the editor

[Klausdk1999]

Recently I needed to implement a way to clear the editor content. I saw there were a few discussions related to it and managed to do this through the ref method, using the ref to the editor and then getting the ref from outside.
I thought about creating a PR to include steps and an example on how to do this.
I could do this in the next weeks, just wanted some opinions, if this is a good idea, if this is the best method to resetting, and should something else be included?

[zbeyens]

Done in https://platejs.org/docs/controlled