release_notes: add swap cancelation feature

Author: carlaKC

release_notes.md

@@ -15,6 +15,14 @@ This file tracks release notes for the loop client.
 ## Next release
 
 #### New Features
+- The loopd client reports off-chain routing failures for loop out swaps if 
+  it cannot find a route to the server for the swap's prepay or invoice payment.
+  This allows the server to release accepted invoices, if there are any, 
+  earlier, reducing the amount of time that funds are held off-chain. If the  
+  swap failed on one of the loop server's channels, it will report failure 
+  location of its off-chain failure. If the failure occurred outside of the 
+  loop server's infrastructure, a generic failure will be used so that no 
+  information about the client's position in the network is leaked.
 
 #### Breaking Changes