message: Document VC++ redistributable requirement
  This fixes
diff: @@ -122,6 +122,9 @@ API. The agent is a single binary (`winpty-agent.exe`) which **must** be in
  the same directory as the Alacritty executable and is available through the
  [GitHub releases page](https://github.com/jwilm/alacritty/releases).
  +On Windows, Alacritty also requires Microsoft's VC++ redistributable to work
  +properly.
  +
  ## Configuration
  Although it's possible the default configuration would work on your system,
  