Add a new Guide: Git Branching strategies - include an ADO version

[j-paquette]

Create a new guide in the docs/_guides folder, using the same format as _template.md

Title: Git Branching strategies - include an ADO version
Content:

Add front matter to this guide, something like this:

---
title: Git Branching strategies - include an ADO version
layout: default
category: Source Control
summary: Add a short description of the guide here.
date: YYYY-MM-DD
---

Add further content here