Run the Azure DevOp packages pipeline nightly (#833)

Schedule the packages build to run once daily at midnight if the source hasn't changed from the last scheduled run. This is typically not needed but currently the build is not being triggered on each merge, so this can act as a way to keep the packages build running consistently.

.azure-pipelines/packages.yml

@@ -5,6 +5,13 @@ trigger:
       - refs/tags/*
 pr: none
 
+schedules:
+- cron: "0 0 * * *"
+  displayName: Daily midnight build
+  branches:
+    include:
+    - master
+
 variables:
   buildConfiguration: release
   dotnetCoreSdkVersion: 3.1.x