Add recipe for loading markdown

[c-w]

This pull request adds a recipe for how to use craco to support loading of markdown into your React application which enables code similar to the following:

import myMarkdownAsHtml from './myMarkdown.md';

const MyComponent = () => <div dangerouslySetInnerHTML={{ __html: myMarkdownAsHtml }} />;

Note that Typescript users should additionally include the following in their index.d.ts file:

declare module '*.md';

[patricklafrance]

Thanks for the recipe :)