README: add contributing guidelines

README.org

@@ -9,19 +9,24 @@ GitLab, for backup and visibility purposes.
 GitLab has a mirroring setting, but it doesn't allow for multiple mirrors, as
 far as I know. I also wanted my instance to be the single source of truth.
 
-* How it works
+** How it works
 
 Gitea is setup to send webhooks to my =lohr= server on every push update. When
 =lohr= receives a push, it clones the concerned repository, or updates it if
 already cloned. Then it pushes the update to *all remotes listed* in the [[file:.lohr][.lohr]]
 file at the repo root.
 
-** Destructive
+*** Destructive
 
 This is a very destructive process: anything removed from the single source of
 truth is effectively removed from any mirror as well.
 
-* Why lohr?
+** Contributing
+
+I accept patches anywhere! Feel free to [[https://github.com/alarsyo/lohr/pulls][open a GitHub Pull Request]], [[https://gitlab.com/alarsyo/lohr/-/merge_requests][a GitLab
+Merge Request]], or [[https://lists.sr.ht/~alarsyo/lohr-dev][send me a patch by email]]!
+
+** Why lohr?
 
 I was looking for a cool name, and thought about the Magic Mirror in Snow White.
 Some *[[https://en.wikipedia.org/wiki/Magic_Mirror_(Snow_White)][furious wikipedia searching]]* later, I found that the Magic Mirror was