Update README.md

Author: Chuxel

containers/docker-existing-dockerfile/README.md

@@ -25,7 +25,7 @@ Follow these steps to use it:
 2. To use VS Code's copy of this definition:
    1. Start VS Code and open your project folder.
    2. Press <kbd>F1</kbd> select and **Remote-Containers: Add Development Container Configuration Files...** from the command palette.
-   3. Select the Existing Dockerfile definition.
+   3. You should be presented with the option to reuse your existing Dockerfile if one is found on the system. Select this to usee the definition.
 
 3. To use latest-and-greatest copy of this definition from the repository:
    1. Clone this repository.