Suggest use of the `fish-plugin` tag to authors (#722)

README.md

@@ -150,6 +150,10 @@ function _ponyo_uninstall --on-event ponyo_uninstall
 end
 ```
 
+### Discoverability
+
+For simplicity and flexibility, Fisher doesn't make use of a central repository of plugins. However, that doesn't mean discovering new plugins should be hard. One convention most popular Fisher plugins on Github follow is [adding](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/classifying-your-repository-with-topics) the topic [fish-plugin](https://github.com/topics/fish-plugin), which puts them on a sortable page of other Fisher plugins.
+
 ## Acknowledgments
 
 Fisher started out in 2016 by [@jorgebucaran](https://github.com/jorgebucaran) as a shell configuration manager for Fish. We had a lot of help along the way. [Oh My Fish](https://github.com/oh-my-fish/oh-my-fish) laid the groundwork as the first popular Fish framework. [@jethrokuan](https://github.com/jethrokuan) was particularly helpful during the first years. [@PatrickF1](https://github.com/PatrickF1)'s candid feedback has been invaluable time and again. Bootstrapping Fisher was originally [@IlanCosman](https://github.com/IlanCosman)'s idea. Thank you to all our contributors! <3