Add documentation how to sync your fork

[ChristianHallerX]

The readme on how to create a Pull Request leaves open how to incorporate all the PullRequests that were made to the repo after forking.
Perhaps we can extend the text on our example repo for anyone who wants to keep up to date with their project.

This is what worked for me:
[(https://www.sitepoint.com/quick-tip-sync-your-fork-with-the-original-without-the-cli/)]

In the "Compare" menu, getting the left and right dropdown in the right direction was a bit a challenge for me, since it is reversed when you open the page. Does someone have a simple solution?

[lazyplatypus]

That's a great idea @ChristianHallerX. Would you mind creating a pull request and link it to this issue?