- Explain which properties are writeable.
- Mark edition-list/N/id as writable.
- Remove (R) from some read-only properties since none of the others
have it.
- Add osd-dimension/ to its subproperties.
- options/<name> isn't read-only.
- focused works on macOS because of 82eda2e. Though it shouldn't be
possible to observe it without raising VO_EVENT_FOCUS.