Add User-Agent header to HTTP requests (#694)

src/LibraryManager/Cache/WebRequestHandler.cs

@@ -60,6 +60,7 @@ private HttpClient CreateHttpClient(string url)
 #pragma warning restore CA2000 // Dispose objects before losing scope
             httpMessageHandler.Proxy = _proxySettings.GetProxy(new Uri(url));
             var httpClient = new HttpClient(httpMessageHandler);
+            httpClient.DefaultRequestHeaders.UserAgent.ParseAdd($"LibraryManager/{ThisAssembly.AssemblyFileVersion}");
 
             return httpClient;
         }