Added css bundle api. Improved css bundling code

I made the code cleaner as requested @Masu-Baumgartner  :>

Moonlight.ApiServer/Services/AssetService.cs

@@ -5,7 +5,6 @@ namespace Moonlight.ApiServer.Services;
 [Singleton]
 public class AssetService
 {
-    public string[] CssFiles { get; private set; }
     public string[] JavascriptFiles { get; private set; }
 
     private bool HasBeenCollected = false;
@@ -22,14 +21,6 @@ public class AssetService
 
     public void CollectAssets()
     {
-        // CSS
-        var cssFiles = new List<string>();
-        
-        cssFiles.AddRange(AdditionalCssAssets);
-        cssFiles.AddRange(PluginService.AssetMap.Keys.Where(x => x.EndsWith(".css")));
-
-        CssFiles = cssFiles.ToArray();
-        
         // Javascript
         var jsFiles = new List<string>();
         
@@ -38,23 +29,10 @@ public class AssetService
 
         JavascriptFiles = jsFiles.ToArray();
     }
-
-    public void AddCssAsset(string asset)
-        => AdditionalCssAssets.Add(asset);
     
     public void AddJavascriptAsset(string asset)
         => AdditionalJavascriptAssets.Add(asset);
 
-    public string[] GetCssAssets()
-    {
-        if (HasBeenCollected)
-            return CssFiles;
-        
-        CollectAssets();
-
-        return CssFiles;
-    }
-
     public string[] GetJavascriptAssets()
     {
         if (HasBeenCollected)