Fix CA1834

.editorconfig

@@ -720,6 +720,9 @@ dotnet_diagnostic.CA1832.severity = warning
 # Use AsSpan or AsMemory instead of Range-based indexers for getting Span or Memory portion of an array.
 dotnet_diagnostic.CA1833.severity = warning
 
+# Use StringBuilder.Append(char) for single character strings.
+dotnet_diagnostic.CA1834.severity = warning
+
 # Prefer the memory-based overloads of ReadAsync/WriteAsync methods in stream-based classes.
 dotnet_diagnostic.CA1835.severity = warning
 

OpenRA.Game/Support/HttpQueryBuilder.cs

@@ -37,7 +37,7 @@ namespace OpenRA.Support
 		{
 			var builder = new StringBuilder(url);
 
-			builder.Append("?");
+			builder.Append('?');
 
 			foreach (var parameter in parameters)
 				builder.Append($"{parameter.Key}={parameter.Value}&");