message: Clarify BASP version documentation
diff: @@ -26,7 +26,7 @@ namespace basp {
  /// @addtogroup BASP
  -/// The current BASP version. Different BASP versions cannot exchange messages.
  +/// The current BASP version. Note: BASP is not backwards compatible.
  constexpr uint64_t version = 3;
  /// @}
  