Add a new docs section "Building a package"

From https://github.com/mesonbuild/meson-python/pull/634#issuecomment-2119236087:

@dnicolodi suggested:
_I wonder whether it is time to have a Building a package top sections in the documentation with the details about build isolation, venv and some hints about cibuildwheel and co for building redistributable wheels._

@rgommers replied:

_Yes, I agree. This is the cause of a lot of the questions/issues we are receiving. I also just searched for `auditwheel` and it's not in our docs (except in the non-public `explanations/design-old.rst`)._

_I won't be able to work on that in the next few days though, since it'll take a few hours at least to do it right. Should we open a new issue for that first, and scope it? I think I'd prefer to address your one comment here, and then have a new PR for the new docs page, containing:_
- _The content added here_
- _Content from `design-old.rst`_
- _Mentioning all the relevant tools._
- _I'd like to refer to https://pypackaging-native.github.io/meta-topics/build_steps_conceptual/#building-and-installing-or-uploading-artifacts, which explains a lot of things that are relevant here._

We do indeed get lots of variations of the same questions that are conceptual issues with how Python packaging works and how `meson-python` fits in. I'm under no illusion that all users are going to understand build isolation and the difference between local and redistributable wheels, but it'd be nice if we could reply with a one-liner linking to the docs.

Beginne mit der Durchsicht der Diskussion im pull request 634 und der vorhandenen nicht öffentlichen Erklärung in design-old.rst. Verwende die verlinkte Seite zu den Build-Schritten für Packaging als Kontext und grenze anschließend einen neuen Dokumentationsabschnitt ab, der Build-Isolation, virtuelle Umgebungen, lokale gegenüber weiterverteilbaren Wheels, cibuildwheel, auditwheel und andere relevante Tools behandelt; als abgeschlossen gilt die Aufgabe, wenn diese Themen erklärt und von der Dokumentation aus verlinkt sind.

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