Add fuzz testing for Section encoding/decoding with multiple edge cases

mapstructure/default.go

@@ -0,0 +1,7 @@
+package mapstructure
+
+var DefaultFormat = NewFormat("mapstructure", WithRequireAll(), WithTrySnakeCase(), WithTryLowCase())
+
+func Decode(data any, v any) error {
+	return nil
+}