Audit and fix `testing-and-debugging.md`

[abatomunkuev]

Hello! I would like to work on testing-and-debugging.md file.
This is a sub-task of issue #18

I will audit and fix based on the following checks:

• Look for any typos
• Make sure all Markdown is correctly done. The conversion was done automatically by a tool, so there may be more idiomatic ways to do some things
• Check the page in a Desktop browser. Does it look OK? Are there any issues that need to be fixed?
• Check the page in a Mobile browser. Does it look OK? Are there any issues that need to be fixed?
• Try the page in both Light and Dark mode. Are there any issues that need to be fixed?
• Try running the page through Lighthouse: https://developers.google.com/web/tools/lighthouse. Are there any issues that need to be fixed?
• Try running the page through Web Hint: https://webhint.io/. Are there any issues that need to be fixed?
• Use alt tags for all images. See https://supercooldesign.co.uk/blog/how-to-write-good-alt-text for suggestions
• Avoid blockquote for indentation, and prefer q or blockquote only when actually quoting. Use Admonitions instead. Example: docs/D-Modulatirty/pointers.md: there are places where > Blockquote are being used and Admonitions could replace it. “Note:” Lightbulb info Admonition.
• Make sure images work in dark and light modes. For example, docs/8-Computations/logic.md Flags image is white background, needs to work in dark. Create a “negative” or SVG so we can do Dark Mode? Can we programmatically create this negative?
• Avoid using <b> and <i> to do emphasis.
• Use backticks and all code for memory addresses and such in tables that use things like void, int, function names, memory addresses.
• Make sure all code blocks use syntax highlighting
• centre images horizontally (esp. when they are small) so they work well at all responsive sizes
• check sub-script and super-script that they are correctly used in all cases
• consider including inter-site links to other pages that have related info
• all links should have descriptive text for accessibility
• Make sure that sub-headings (right-hand side) for each document are correct.
• Improve readability of code comments (i.e., // and /*...*/) in dark mode (even light mode might need some work)
• Fix Frontmatter for page to include proper id, title, slug, etc.