[bazel.build] Problem with /start/cpp - MODULE.bazel

### Page link:

https://bazel.build/start/cpp

### Problem description (include actual vs expected text, if applicable):

The tutorial tells you that the MODULE.bazel file is what identifies the directory as a workspace and is where you specify dependencies. It would be useful to have a brief description of the contents in the example one, too.

### Where do you see this issue? (include link to specific section of the page, if applicable)

https://bazel.build/start/cpp#getting-started

### Any other information you'd like to share?

_No response_

Open https://bazel.build/start/cpp#getting-started and review the linked C++ tutorial, especially the example MODULE.bazel file. Add a brief description of that example's contents where the page currently explains its purpose, then verify that the wording is clear in the rendered tutorial.

Written by the indexing model from the issue text.