Add more information and requirements to README.md (#79)

README.md

@@ -6,6 +6,18 @@ This project is built using [react-admin](https://marmelab.com/react-admin/).
 
 It needs at least Synapse v1.18.0 for all functions to work as expected!
 
+You get your server version with the request `/_synapse/admin/v1/server_version`.
+See also [Synapse version API](https://github.com/matrix-org/synapse/blob/develop/docs/admin_api/version_api.rst).
+
+After entering the URL on the login page of synapse-admin the server version appears below the input field.
+
+
+You need access to the following endpoints:
+- `/_matrix`
+- `/_synapse/admin`
+
+See also [Synapse administration endpoints](https://github.com/matrix-org/synapse/blob/develop/docs/reverse_proxy.md#synapse-administration-endpoints)
+
 ## Step-By-Step install:
 
 You have two options: