Update documenting.qmd with tools::checkRd section

[7se7en72025]

Adds a new section on checking Rd files using tools::checkRd to documenting.qmd.

Provides practical usage examples, explanations of typical errors caught, and instructions for using the function

Includes code blocks for R syntax highlighting and output samples

Improves clarity for contributors on how to validate Rd documentation before package submission

Addresses issue #164 and follows best practices for documentation maintenance

This change helps maintain documentation quality and makes it easier for others to understand and apply Rd file validation.

Summary
This pull request adds a dedicated section to documenting.qmd that guides contributors in validating .Rd documentation files with tools::checkRd. The problem addressed is that not all contributors are aware of tools available to check their documentation for errors before submitting packages. With real-world examples and explained error output, it is now easier to catch issues early.

Specific changes:
Added “Checking Rd Files with tools::checkRd” section with usage, examples, and error/output descriptions

Used fenced code blocks for better readability and R syntax highlighting

Improved documentation workflow explanation for new contributors

Fixes #164

Checklist for adding a new chapter or chapters
Have you updated the Quick start to the guide accordingly?

Have you updated the chapters field of _quarto.yml? This determines the chapter ordering.

Have you named the new .qmd files using lower case, with words separated by _ if required?

What should a reviewer concentrate their feedback on?
Clarity and accuracy of new section on tools::checkRd

Code block formatting and example execution/output

Placement of the section within the overall documentation flow

Acknowledging contributors
@7se7en72025
For reviewers: All relevant contributions have been added, including reviewers, mentors, contributors to the ideas/planning.