chore: Move editor into codebase (#2930)

shared/editor/commands/README.md

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+https://prosemirror.net/docs/ref/#commands
+
+Commands are building block functions that encapsulate an editing action. A command function takes an editor state, optionally a dispatch function that it can use to dispatch a transaction and optionally an EditorView instance. It should return a boolean that indicates whether it could perform any action.
+
+Additional commands that are not included as part of prosemirror-commands, but are often reused can be found in this folder.