Improved documentation

Author: JohanMabille

include/xsimd/types/xsimd_api.hpp

@@ -486,7 +486,9 @@ namespace xsimd
     /**
      * @ingroup batch_data_transfer
      *
-     * Creates a batch from the single value \c v.
+     * Creates a batch from the single value \c v. If \c v is a boolean,
+     * this function returns a batch_bool<uint8_t>. If you need another type
+     * of batch_bool, please use broadcast_as instead.
      * @param v the value used to initialize the batch
      * @return a new batch instance
      */