Update RELEASE.md (#603)

Include information on pushing packages through the respective release.

RELEASE.md

@@ -30,9 +30,13 @@ In this example, the version for the release is **11.1.17**.
 Create a new release at https://github.com/microsoft/slngen/releases.  The tag must be in the format of vMAJOR.MINOR.BUILD (The tag must start with a lead **v**). Using the above example, the tag would be `v11.1.17`.  Release notes
  should contain the important commits that are relevant to that release and can be auto-generated by GitHub.  You can leave out commits that are not customer facing.
 
+## Push packages
+
+Approve the stages corresponding to the [SlnGen release](https://devdiv.visualstudio.com/DevDiv/_release?definitionId=3478) with the correct tag to push non-CoreXT packages to nuget.org and CoreXT packages to the CloudBuild feed.
+
 Packages published to nuget.org use an Azure DevOps Service Connection [1ES-NuGet-Full](https://dev.azure.com/devdiv/DevDiv/_settings/adminservices?resourceId=841455b3-9379-4c8a-89a3-ec3ba7747d31).  The API key is good for one year
  and will need to be regenerated when it expires.  If a release fails, you will need to update the service connection with a new API key and re-run the deploy stage.
 
 Packages published to the internal Azure DevOps Artifacts Services feed, specifically the CoreXT packages, use an Azure DevOps Service Connection [CloudBuild-Push](https://dev.azure.com/devdiv/DevDiv/_settings/adminservices?resourceId=da914f0a-3a04-4d03-b5dd-b54c2b715c00).
   If a push fails, you will need to regenerate a Personal Access Token with permissions to push to the [CloudBuild](https://dev.azure.com/cloudbuild/CloudBuild/_packaging?_a=feed&feed=CloudBuild) feed and update the PAT in the
-  service connection.
+  service connection.