Point to the migration guide from `README.md`
-<details>
- <summary>FYI: Updating from v0.3.4 to v0.4.0</summary>
-
- - `answer_str` -> `answer`
- - `msg.text_owned()` -> `msg.map(ToOwned::to_owned)`
- - Use `.auto_send()` to construct your bot: `let bot = Bot::from_env().auto_send();`. This allows not to write `.send()` after each request; now it is done automatically. Also, rewrite `UpdateWithCx<Message>` -> `UpdateWithCx<AutoSend<Bot>, Message>`.
- - `ResponseResult<()>` -> `Result<(), Box<dyn Error + Send + Sync>>` (or import `ResponseResult` beforehand: `use teloxide::requests::ResponseResult;`)
- - Tokio updated to v1.2.
-
-Note: this list is non-exhaustive; for the full list of changes, see the [teloxide-core changelog] and [teloxide changelog].
-
-[teloxide-core changelog]: https://github.com/teloxide/teloxide-core/blob/master/CHANGELOG.md
-[teloxide changelog]: CHANGELOG.md
-
-</details>
+[v0.4.0 => v0.5.0 migration guide >>](MIGRATION_GUIDE.md)
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