Docs: add a link to the source code for each utility

[takanome-dev]

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Add a link to the source code for each utility. Since every H4 element in the doc source files is a heading for a utility we can attach these links by dynamically attaching the heading title to a path pattern to the repository

As you can see above, source and npm package are links that lead to external resources. In this case, we only need to link to the source. Also, notice how the details for each component are laid out in a well-spaced manner making readability a breeze. All the utilities are documented using a uniform schema containing the fields:

• Parameters
• Description
• Returns
• Example

Maybe a React component to template this layout would be efficient.