Extended to parse different types of data

Added methods to parse comments for type definitions and examples of typical usage.

**Example:**
A user can define a mixin:

```css
/*
@mixin

A mixin to apply border-radius.

Usage:
@include border-radius(5px);
@include border-radius(2px 4px 2px 4px);

Styleguide Mixins.BorderRadius.
*/
@mixin border-radius($args...) {
  ...
}
```

Or an extendable class:
```css
/*
@extend

Makes elements look like buttons.

Usage:
@extend %button;

Styleguide Extends.Button.
*/
%button {
  ...
}
```

This will allow users to render lists of available mixins, extendable classes, variables etc.

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If theres any recommendations/things I've missed - just leave a comment :grinning: