[doc] release-process: Mention GitHub release and archived release notes

Author: MarcoFalke

doc/release-process.md

@@ -280,6 +280,8 @@ bitcoin.org (see below for bitcoin.org update instructions).
 
   - Notify BlueMatt so that he can start building [the PPAs](https://launchpad.net/~bitcoin/+archive/ubuntu/bitcoin)
 
-  - Add release notes for the new version to the directory `doc/release-notes` in git master
+  - Archive release notes for the new version to `doc/release-notes/` (branch `master` and branch of the release)
+
+  - Create a [new GitHub release](https://github.com/bitcoin/bitcoin/releases/new) with a link to the archived release notes.
 
   - Celebrate