add redirect (#260)

Author: mongoKart

config/redirects

@@ -1,6 +1,6 @@
 define: prefix docs/drivers/csharp
 define: base https://www.mongodb.com/${prefix}
-define: versions v2.19 v2.20 v2.21 v2.22 v2.23 v2.24 v2.25 v2.26 v2.27 v2.28 v2.29 v2.30 master
+define: versions v2.19 v2.20 v2.21 v2.22 v2.23 v2.24 v2.25 v2.26 v2.27 v2.28 v2.29 v2.30 v3.0 master
 
 symlink: current -> master