Create Getting Started with Qt Bridges for C#/.NET

As a user, I would like to read how to get started with the Qt Bridges for C#/.NET. Some of the topics can include:

• Getting started: Introduction to the project with goals and scope
• Getting started: Creating a new app (Visual Studio Code and command-line)
• Getting started: Running the app
• Getting started: A note on the Qt Quick Controls that can be used
• Getting started: How to add tests to the app

Use QDoc to generate the documentation. Let's figure out how linking to the C# entities will work once the documentation is established.

Note that this is only overview documentation, written in .qdoc files, not reference documentation, which will be generated from a language-specific toolchain.