Update CONTRIBUTING.md
Add the --recurse-submodules option to the git clone command.
@@ -27,7 +27,7 @@ pull requests (PRs).
To create a new PR, fork the project in GitHub and clone the upstream repo:
```sh
-$ git clone https://github.com/microsoft/cpp_client_telemetry.git
+$ git clone --recurse-submodules https://github.com/microsoft/cpp_client_telemetry.git
```
Add your fork as an origin:
