fix(docs): correct typo in the 'Configure startup file' section of in…

…stallation guide

Changed method call from AddLumexService() to AddLumexServices()
to reflect updated API or improved functionality representation.

docs/LumexUI.Docs.Client/Samples/Installation/installationServices.html

@@ -1,4 +1,4 @@
 <pre><code class="language-csharp">using LumexUI.Extensions;
 
-builder.Services.AddLumexService();
+builder.Services.AddLumexServices();
 </code></pre>