Add description and embedded css to POS (#970)

* Add description and embedded css to POS

* wrap embedded css props in <style> before Safe.raw

BTCPayServer/Controllers/AppsPublicController.cs

@@ -87,7 +87,9 @@ namespace BTCPayServer.Controllers
                 CustomTipText = settings.CustomTipText,
                 CustomTipPercentages = settings.CustomTipPercentages,
                 CustomCSSLink = settings.CustomCSSLink,
-                AppId = appId
+                AppId = appId,
+                Description = settings.Description,
+                EmbeddedCSS = settings.EmbeddedCSS
             });
         }