Add link to Martin Fowlers git patterns page

[HonkingGoose]

Closes #1434

[HonkingGoose]

Hi @ben, here's your pull-request! 🚀

• I tried to give a overview of why the page is worth reading, but it might be too verbose for the book.
• I also offered my advice on at least reading the Integration Frequency section.

I'm not too sure what's the best place for the link, up top, or after the explanation.

So I'm eagerly awaiting your feedback, and your recommended changes. 😄

[ben]

Yes! This fits in pretty well in this section of the book. I have two requests:

1. Can we make this shorter, and structure it as a [[NOTE]]? It's not our content, so we should call it out with formatting as a pointer to something else.
2. Let's drop the list of topics. It will inevitably get out of date, and having to follow that project in order to keep this one correct is a chore I don't think anyone wants.

[HonkingGoose]

I've made the changes you wanted.

However I also noticed that we already have a section of the book with some of the workflows:
https://github.com/progit/progit2/blob/master/book/05-distributed-git/sections/distributed-workflows.asc

Do you still want the link to be where it would be now, or would you rather move it to just before the summary of distributed workflows section of the book?

I've marked the pull-request as a draft, so that we only merge it if we're happy with it. 😄

[ben]

Oh, hmm. Now that you mention it, this content really does belong in chapter 5. Chapter 3's section is meant to introduce the idea of branches, but mostly in a repo-local context. The multi-repo model is in chapter 5, and I think that's where these workflows belong, I think. Can we relocate this note to the summary area of that section in chapter 5?

[HonkingGoose]

@ben I moved the text to just before the summary in chapter 5. I also trimmed the text a bit.

[ben]

Great, thanks!