(maint) Add Community Validation Extension to build script

This updates the appveyor build script to ensure that all packaged
packages will comply with the requirements defined in the newly
released extension that validates packages for use with CCR.

.appveyor.yml

@@ -62,6 +62,7 @@ install:
       'wormies-au-helpers' = '0.4.1'
       'chocolatey-core.extension' = '1.4.0'
       'autohotkey.install' = '1.1.35.00'
+      'chocolatey-community-validation.extension' = '0.1.0'
     }.GetEnumerator() | % {
       if (!(Test-Path "${env:nupkg_cache_path}\$($_.Key).$($_.Value).nupkg")) { rm "${env:nupkg_cache_path}\$($_.Key).*.nupkg" ; iwr "https://chocolatey.org/api/v2/package/$($_.Key)/$($_.Value)" -OutFile "${env:nupkg_cache_path}\$($_.Key).$($_.Value).nupkg" }
       if ($_.Key -eq 'chocolatey') { cup $_.Key --version $_.Value --source ${env:nupkg_cache_path} --allow-downgrade --pre }