Merge pull request #5865 from dotnet/dev/lerich/readme-updates

Update README.md to notify user about .NET Runtime Tool

Author: leslierichardson95

README.md

@@ -8,6 +8,7 @@ While it is possible to use the C# extension as a standalone extension, we highl
 
 1. Installing [C# Dev Kit][csdevkitextension] will automatically install this extension as a required dependency
 2. Open a folder/workspace that contains a C# project (.csproj) and a C# solution (.sln) and the extension will activate.
+3. Whether you install C# Dev Kit or just the C# extension, the [.NET Runtime Installer Tool extension](https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.vscode-dotnet-runtime) will be installed as a dependency.
 
 Note: If working on a solution that requires versions prior to .NET 6, install a Full Framework runtime and MSBuild tooling.
   * Set omnisharp.useModernNet to false and if you are on the pre-release verion, set dotnet.server.useOmnisharp to true
@@ -69,4 +70,4 @@ If someone has already filed an issue that encompasses your feedback, please lea
 Let us know what you think of the extension by taking the quick survey.
 
 
-[csdevkitextension]: https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.csdevkit
+[csdevkitextension]: https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.csdevkit