document the future breaking change process

Author: aignas

CONTRIBUTING.md

@@ -196,15 +196,11 @@ The general process is:
 Note that the `+1` and `+2` releases are just examples; the steps are not
 required to happen in immediately subsequent releases.
 
-:::{todo}
-TODO: clarify this before releasing `1.0`
-
-Maybe:
+Once The first major version is released, the process will be:
 1. In `N.M.0` we introduce the new behaviour, but it is disabled by a feature flag.
 2. In `N.M+1.0` we may choose the behaviour to become the default if it is not too
    disruptive.
-3. In `N+1.0.0` we get rid of the old behaviour
-:::
+3. In `N+1.0.0` we get rid of the old behaviour.
 
 ### How to control breaking changes