Incorrect requirements documented

[karl-cardenas-coding]

The docs state --initialDocURLs as the only required parameter. That's incorrect.

[archiewood]

For those that need to know, min requirements are:

npx docs-to-pdf docusaurus --initialDocURLs="https://docusaurus.io/docs" --contentSelector "article" --paginationSelector="a.pagination-nav__link--next"