Rename docs/rollback.md to docs/features/rollback.md (argoproj#2438)

fixing 404 https://argoproj.github.io/argo-rollouts/features/rollback.md - put it in the expected location

Signed-off-by: Alex Eftimie <[email protected]>

Signed-off-by: Alex Eftimie <[email protected]>

Author: alexef

docs/rollback.md renamed to docs/features/rollback.md

@@ -20,4 +20,4 @@ spec:
   revisionHistoryLimit: 5
 ```
 
-Assume a linear revision history: `1`, `2`, `3`, `4`, `5 (current)`. A rollback from revision 5 back to 4 or 3 will fall within the window, so it will be fast tracked.
+Assume a linear revision history: `1`, `2`, `3`, `4`, `5 (current)`. A rollback from revision 5 back to 4 or 3 will fall within the window, so it will be fast tracked.