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.Client/Models/AssetPairData.cs

@@ -8,7 +8,7 @@ public class AssetPairData
     public AssetPairData()
     {
     }
-    
+
     public AssetPairData(string assetBought, string assetSold, decimal minimumTradeQty)
     {
         AssetBought = assetBought;
@@ -25,7 +25,7 @@ public class AssetPairData
     [JsonProperty]
     public decimal MinimumTradeQty { set; get; }
 
-    
+
     public override string ToString()
     {
         return AssetBought + "/" + AssetSold;