Compatibility with Marked's extension system

[kazk]

Export the extension as a custom Renderer class (or a function that returns an object with Renderer interface) so that it's compatible with Marked's extension system.

Instead of

process(marked, markdown, { language: 'javascript' });

do

marked(markdown, { renderer: new Renderer({ language: 'javascript' }) });
marked(markdown, { renderer: renderer({ language: 'javascript' }) });

This way, we can override or adjust something when necessary in our apps, or experiment before including it here. This also makes some options like extensions unnecessary.

[jhoffner]

We might want to rename extensions to something else, like blockExtensions – since they are really about extending the block syntax and we need to know the extension name (otherwise we will assume it is a language).

[kazk]

extensions shouldn't be necessary if we make it compatible. This extension shouldn't be handling them.

If I'm understanding how Marked's extension works correctly, users can either:

• do marked.use(thisExtension, customExtension). customExtension provides new %foo, then fall backs to this extension for anything else.
• create CustomRenderer that inherits from this extension's Renderer that handles anything new and fall backs to this extension.

If the extension needs something like afterRender. It can be exposed from the custom renderer that extends this one.

const renderer = new CustomRenderer(options); // inherits from this extension's
const html = marked(markdown, { renderer });
// After inserting to document
renderer.afterRender();

[JulianLang]

I like the idea for the given reasons, too. Are there any updates?