Code formatting updates (#4502)

* Editorconfig: Add space_before_self_closing setting

This was a difference between the way dotnet-format and Rider format code. See https://www.jetbrains.com/help/rider/EditorConfig_Index.html

* Editorconfig: Keep 4 spaces indentation for Swagger JSON files

They are all formatted that way, let's keep it like that.

* Apply dotnet-format, mostly white-space related changes

BTCPayServer/Models/StoreViewModels/RatesViewModel.cs

@@ -16,7 +16,7 @@ namespace BTCPayServer.Models.StoreViewModels
             public string Rule { get; set; }
             public bool Error { get; set; }
         }
-        
+
         public void SetExchangeRates(IEnumerable<AvailableRateProvider> supportedList, string preferredExchange)
         {
             supportedList = supportedList.Select(a => new AvailableRateProvider(a.Id, a.SourceId, a.DisplayName, a.Url, a.Source)).ToArray();