Update Getting Started

Nobody has claimed this yet.

Right now the [Getting Started](https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit#-getting-started) section in the README is a bit outdated.

People who are just getting started with this library are not likely to have all of the [dependencies needed](https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/wiki/Compiling-From-Source) (latest version of VS, .NET Core, etc.) to compile the source code and demo application.

I am looking for people newer to this project to either comment or submit a PR with suggestions on how to improve this.

Some ideas to consider:
- Getting started section so that it is as simple as possible for someone new to the library.
- ~Consider including a link to my [examples repo](https://github.com/Keboo/MaterialDesignInXaml.Examples)~
- Consider moving up the link to the releases page with the pre-compiled demo app from the [See It In Action section](https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit#-see-it-action)
- Remove the [Source Code section](https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit?tab=readme-ov-file#building-the-source) and instead simply link over to the [wiki page](https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/wiki/Compiling-From-Source)

Review the README's Getting Started, See It In Action, and Building the Source sections, along with the linked Compiling From Source wiki page. Update the onboarding guidance so prerequisites and the pre-compiled demo are easy to find, and ensure source-building instructions point to the wiki; done means a newcomer can follow the documented path without outdated setup information.

Written by the indexing model from the issue text.