Generate a HTML doc and host it online

Hi!

Let's use [docfx](https://dotnet.github.io/docfx/) to generate a static documentation for Cardizer.

> DocFX is an API documentation generator for .NET, which currently supports C#, VB and F#. It generates API reference documentation from triple-slash comments in your source code. It also allows you to use Markdown files to create additional topics such as tutorials and how-tos, and to customize the generated reference documentation. DocFX builds a static HTML website from your source code and Markdown files.

Then to we could host it on a web server (for example, github.io).