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/Forms/ModifyForm.cs

@@ -5,7 +5,7 @@ namespace BTCPayServer.Forms;
 public class ModifyForm
 {
     public string Name { get; set; }
-    
+
     [DisplayName("Form configuration (JSON)")]
     public string FormConfig { get; set; }
 }