Improve CI setup (#23)

* Use latest ADO images
* Run CI builds daily, to detect failures more quickly

Author: lupino3

azure-pipelines.yml

@@ -8,16 +8,24 @@ trigger:
       - examples/*
       - .gitignore
 
+schedules:
+- cron: "0 0 * * *"
+  displayName: Daily CI build
+  always: true
+  branches:
+    include:
+    - master
+
 jobs:
 - job: PowerShellCore
   strategy:
     matrix:
       linux:
-        imageName: 'ubuntu-16.04'
+        imageName: 'ubuntu-18.04'
       mac:
         imageName: 'macos-10.15'
       windows:
-        imageName: 'vs2017-win2016'
+        imageName: 'windows-2019'
 
   pool:
     vmImage: $(imageName)