Update LanguageSettings.ps1 (Azure#17317)

* Add function to retrieve package versions from nuget

* Add SetPackageVersion function, update call to Update-ChangeLog.ps1

* Add GetPackageInstallNotes functions

* Add GeneralReleaseNotesParser.ps1 script

Author: chidozieononiwu

eng/scripts/Language-Settings.ps1

@@ -223,4 +223,16 @@ function SetPackageVersion ($PackageName, $Version, $ServiceDirectory, $ReleaseD
   }
   & "$EngDir/scripts/Update-PkgVersion.ps1" -ServiceDirectory $ServiceDirectory -PackageName $PackageName `
   -NewVersionString $Version -ReleaseDate $ReleaseDate
+}
+
+function GetExistingPackageVersions ($PackageName, $GroupId=$null)
+{
+  try {
+    $existingVersion = Invoke-RestMethod -Method GET -Uri "https://api.nuget.org/v3-flatcontainer/${PackageName}/index.json"
+    return $existingVersion.versions
+  }
+  catch {
+    LogError "Failed to retrieve package versions. `n$_"
+    return $null
+  }
 }