bug: Table of contents links jump from Heading Level 1 to 4

[colinkiama]

What Happened?

The heading levels should increment gradually (1, 2, 3...). This should not be happening:

This is not something that is valid in the generated HTML..

We could reproduce the same h4 styling on <ul> and <li> elements with a class rules instead.

Steps to Reproduce

View the following file in the repository: `tutorials/programming-language/main/03-00-object-oriented-programming.md`

Web Browser

Google Chrome

Operating System / Version

Windows 11

Additional Information

• markdownlint Rule MD001 - Header levels should only increment by one level at a time
• MDN - <h1>–<h6>: The HTML Section Heading elements
• HTML Living Standard - The h1, h2, h3, h4, h5, and h6 elements

[colinkiama]

This issue was initially discovered here: #110 (comment)