feat(content): add path for custom parsers

[btkostner]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

This PR adds a second param for custom parsers that is an object (for future extend-ability) with the file path.

Here is my use case:

I'm building a photography portfolio website where I want to drop images in the content folder. I have a custom parser that extracts metadata from the jpg. Sadly I can't get the utf-8 read file content to parse correctly on any of the packages I have found on npm. Most of them just take the file path and handle the reading themselves.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes (if not applicable, please state why)