[INFRA] Addition of basic contributor guides and docs framework. (#5581)

* Addition of basic contributor docs.

- Main contributor guide landing page.
- C# codestyle doc.
- Pull request guide doc.

All files and structure heavily inspired by the dotnet/runtime docs: https://github.com/dotnet/runtime/tree/main/docs

* fix typos and review changes

* Update XML doc requirement & conversation review.

docs/README.md

@@ -0,0 +1,40 @@
+# Documents Index
+
+This repo includes several documents that explain both high-level and low-level concepts about Ryujinx and its functions. These are very useful for contributors, to get context that can be very difficult to acquire from just reading code.
+
+Intro to Ryujinx
+==================
+
+Ryujinx is an open-source Nintendo Switch emulator, created by gdkchan, written in C#. 
+* The CPU emulator, ARMeilleure, emulates an ARMv8 CPU and currently has support for most 64-bit ARMv8 and some of the ARMv7 (and older) instructions.
+* The GPU emulator emulates the Switch's Maxwell GPU using either the OpenGL (version 4.5 minimum), Vulkan, or Metal (via MoltenVK) APIs through a custom build of OpenTK or Silk.NET respectively.
+* Audio output is entirely supported via C# wrappers for SDL2, with OpenAL & libsoundio as fallbacks.
+
+Getting Started
+===============
+
+- [Installing the .NET SDK](https://dotnet.microsoft.com/download)
+- [Official .NET Docs](https://docs.microsoft.com/dotnet/core/)
+
+Contributing (Building, testing, benchmarking, profiling, etc.)
+===============
+
+If you want to contribute a code change to this repo, start here.
+
+- [Contributor Guide](../CONTRIBUTING.md)
+
+Coding Guidelines
+=================
+
+- [C# coding style](coding-guidelines/coding-style.md)
+- [Service Implementation Guidelines - WIP](https://gist.github.com/gdkchan/84ba88cd50efbe58d1babfaa7cd7c455)
+
+Project Docs
+=================
+
+To be added. Many project files will contain basic XML docs for key functions and classes in the meantime.
+
+Other Information
+=================
+
+- N/A