feat(checkver): Present script property (#3900)

bin/checkver.ps1

@@ -196,8 +196,11 @@ while ($in_progress -gt 0) {
     $expected_ver = $json.version
     $ver = ''
 
-    $err = $ev.SourceEventArgs.Error
     $page = $ev.SourceEventArgs.Result
+    $err = $ev.SourceEventArgs.Error
+    if ($json.checkver.script) {
+        $page = $json.checkver.script -join "`r`n" | Invoke-Expression
+    }
 
     if ($err) {
         next "$($err.message)`r`nURL $url is not valid"

schema.json

@@ -260,6 +260,10 @@
                         },
                         "useragent": {
                             "type": "string"
+                        },
+                        "script": {
+                            "$ref": "#/definitions/stringOrArrayOfStrings",
+                            "description": "Custom PowerShell script to retrieve application version using more complex approach."
                         }
                     },
                     "type": "object"