Ticket #23778 -- Add a code snippet in the advanced testing documentatio...

...n showing how to run tests outside de test runner.
And thirdly, I think that the word "project" should be left out of this doc addition. Generally a Django project has a `manage.py` so you don't need this script. In most cases when you do, the reason is because you are writing a test script for a reusable app, in the absence of a "project". So references to `my_project` are just confusing; I would replace it `'myapp.tests.test_settings'` or similar.

(Yes, I realize that it's also possible to write a script like this to run tests in a "sample project" bundled with a reusable app, and that may be the situation you have, but I think in general it is less common. If we show the more general technique, it's not hard to see how to apply it to that case.)