Add Debugging Guidance to README

[Burtannia]

Updated the README based on #1796 and enshrined the guidance given by #1711 (comment) into documentation.

Hopefully goes part of the way to addressing #1794.

Also adds a note that if build-system is not specified then it defaults to setuptools whereas the example in the README uses Hatch. As a newcomer to Python I didn't understand this which made it even harder to figure out what was wrong with my pyproject.toml file. To mitigate this for future users I've included a link to the pyproject.toml page of the setuptools documentation.

Contributor checklist

• Provided the tests for the changes. (N/A, documentation change)
• Assure PR title is short, clear, and good to be included in the user-oriented changelog

Maintainer checklist

• Assure one of these labels is present: backwards incompatible, feature, enhancement, deprecation, bug, dependency, docs or skip-changelog as they determine changelog listing.
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[atugushev]

We can just fix the code since build addressed the issue (not released yet).

Shout-out to @q0w 🎉

[keithly]

The first paragraph (about what happens when no build tool is specified) is still useful information. I was confused by that the first time I used pip-tools.

[webknjaz]

Please, don't add trailing spaces to lines.

[webknjaz]

Hi, this would need a migration to Markdown, if still relevant.

[atugushev]

Superseded by #1979.