message: Add a note about the build required to the README
diff: ## Installation
  +_(Note: in order to run the Windows Terminal, you'll need to be running at least Windows build 18362 or higher.)_
  +
  ### Microsoft Store
  Download the Microsoft Terminal free from the Microsoft Store and it'll be continuously updated. Or, feel free to side-load [releases](https://github.com/microsoft/terminal/releases) from GitHub, but note they won't auto-update.
  