add xamarin tool version

get-new-tool-versions/parsers/xamarin-parser.psm1

@@ -0,0 +1,30 @@
+using module "./base-parser.psm1"
+
+class XamarinVersionsParser: BaseVersionsParser {
+    [PSCustomObject] GetAvailableVersions() {
+        $allVersions = $this.ParseAllAvailableVersions()
+        return $allVersions
+    }
+
+    [hashtable] GetUploadedVersions() {
+        $url = $this.BuildGitHubFileUrl("actions", "virtual-environments", "main", "images/macos/toolsets/toolset-11.0.json")
+        $releases = Invoke-RestMethod $url -MaximumRetryCount $this.ApiRetryCount -RetryIntervalSec $this.ApiRetryIntervalSeconds
+        $xamarin = $releases.xamarin
+        $xamarinReleases = @{
+            'Mono Framework' = $xamarin.'mono-versions'
+            'Xamarin.Android' = $xamarin.'android-versions'
+            'Xamarin.iOS' = $xamarin.'ios-versions'
+            'Xamarin.Mac' = $xamarin.'mac-versions'
+        }
+        return $xamarinReleases
+    }
+
+    hidden [PSCustomObject] ParseAllAvailableVersions() {
+        $url = "http://aka.ms/manifest/stable"
+        $filteredProducts = @('Mono Framework', 'Xamarin.Android', 'Xamarin.iOS', 'Xamarin.Mac')
+        $releases = Invoke-RestMethod $url -MaximumRetryCount $this.ApiRetryCount -RetryIntervalSec $this.ApiRetryIntervalSeconds
+        $items = $releases.items
+        $products = $items | Where-Object {$_.name -in $filteredProducts} | Sort-Object name | Select-Object name, version
+        return $products
+    }
+}