How to serialize/deserialize text editors and structures including text editors

Put up a PR to improve documentation (as per issue @shhyou raised). @alexh I referenced your solution in the docs, one step below an addition to the library. Tagging so you're aware of this :grin:

Link: [Docs] Clarify `write-to-file` and `read-from-file` Behavior by robertDurst 路 Pull Request #359 路 racket/gui 路 GitHub