Include the functionality of the plugins in the demo or link to them in the README

[j-a-m-l]

When I find this project I thought that my search was finished because I want to include some custom syntax in my md files.

But when I tried the demo I was disappointed because several features that are supported by the markdown-it.js version wasn't working (tasks, tables, etc.).

Later I've discover the plugins in https://github.com/markdown-it-rust/markdown-it-plugins.rs, which cover some of these functionalities.

I think that adding a link in the README would be very useful. It'd be also very useful including the plugins as optional features (just a checkbox to enable or disable the plugin).