message: Changelog.md: wording change
diff: - Fixes SEGV when closing the terminal via GUI close button.
  - Fixes scrolling in alt-screen.
  - Fixes VT sequence for setting indexed color from palette.
  -- Fixes `XTSMGRAPHICS` when querying sixel image limits, to be capped at terminal viewport dimensions (#656).
  +- Changes `XTSMGRAPHICS` to match implementation of xterm *exactly* when querying sixel image limits, to be capped at terminal viewport dimensions (#656).
  - Win32: Attaches to parent console if present, so typing `contour help` in a terminal actually shows something.
  - Implements UTF-8 encoded mouse transport (`CSI ? 1005 h`)
  - Improved vi-like input modes.
  