docs: add dev docs links to the README

README.md

@@ -14,8 +14,11 @@ Poise is an opinionated Discord bot framework with a few distinctive features:
 
 # How to use
 
-Most information is in the [API documentation](https://docs.rs/poise/). Also take a look at the
-[examples](examples), especially `feature_showcase`, to learn what poise can do.
+Most information is in the [API documentation](https://docs.rs/poise/). If you're using a
+development version, you probably want to look at the documentation for
+[`current`](https://serenity-rs.github.io/poise/current), [`next`](https://serenity-rs.github.io/poise/next)
+or [`serenity-next`](https://serenity-rs.github.io/poise/serenity-next) branch instead. Also take a
+look at the [examples](examples), especially `feature_showcase`, to learn what poise can do.
 
 For further questions, don't hesitate to join the support server: https://discord.gg/serenity-rs.