Add documentation for new sliding-sync setup and upgrade info

Author: dali99

MIGRATIONS.MD

@@ -2,6 +2,11 @@
 
 This is a best effort document descibing neccecary changes you might have to do when updating
 
+## 0.6.1
+
+enableSlidingSync, and setting matrix-synapse.sliding-sync.environmentFile (or any other sliding-sync setting)
+is no longer needed for a sliding-sync setup. Upgrading will force relogins for all users.
+
 ## 0.5.0
 
 * The module has been renamed from `synapse` to `default`

README.MD

@@ -38,19 +38,3 @@ With matrix.YOURDOMAIN pointing at the server:
 ```
 
 is ~enough to get a functional matrix-server running with some workers
-
-## Sliding Sync (Element X)
-
-Just add the following to your config and point `slidingsync.YOURDOMAIN` at the server
-
-```
-services.matrix-synapse-next = {
-  enableSlidingSync = true;
-};
-
-services.matrix-synapse.sliding-sync.environmentFile = "/some/file/containing/SYNCV3_SECRET=<some secret>";
-
-```
-
-If using [well-known delagation](https://matrix-org.github.io/synapse/v1.37/delegate.html) make sure `YOURDOMAIN/.well-known/matrix/client` matches
-what's in `matrix.YOURDOMAIN/.well-known/matrix/client`