message: rle: fix build with clang by adding a deduction guide
diff: @@ -1013,6 +1013,9 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
  #ifdef UNIT_TESTING
  friend class ::RunLengthEncodingTests;
  #endif
  +
  + template<typename It>
  + rle_scanner(It b, It e) -> rle_scanner<It>;
  };
  template<typename T, typename S = std::size_t>
  