message: updated README.md to clarify that another extension is needed as a dependency
diff: powerful configure+build workflow for CMake-based projects within the
  Visual Studio Code editor.
  -This extension itself *does not* provide language support for the CMake
  -scripting language. For that I recommend [this extension](https://marketplace.visualstudio.com/items?itemName=twxs.cmake).
  +Make you have [this dependency](https://marketplace.visualstudio.com/items?itemName=twxs.cmake) installed before using CMake Tools.
  ## What's New?
  