Update publish-website.yaml for Azure Pipelines

Author: kevin-carroll

build/publish-website.yaml

@@ -14,7 +14,7 @@
 # the "master" branch witch is then hosted by github pages
 
 pool:
-    vmImage: ubuntu-18.04
+    vmImage: ubuntu-20.04
 
 steps:
     - task: NodeTool@0