Update pyproject.toml

- be more clear that the values in [build-system] may be generated by the command line interface of the build backend, so the [build-system] table is not required
- reorganize comments to better correspond to their sections

pyproject.toml

@@ -1,24 +1,24 @@
-# pyproject.toml specification:
+# Specification of pyproject.toml:
 # https://packaging.python.org/en/latest/guides/writing-pyproject-toml/
 
 # Should pyproject.toml be added?
-# https://packaging.python.org/en/latest/guides/modernize-setup-py-project/#should-pyproject-toml-be-added
 # A pyproject.toml file is strongly recommended. The presence of a pyproject.toml 
 # file itself does not bring much. What is actually strongly recommended is the 
 # [build-system] table in pyproject.toml.
+# https://packaging.python.org/en/latest/guides/modernize-setup-py-project/#should-pyproject-toml-be-added
 
 # Choosing a build backend:
 # https://packaging.python.org/en/latest/tutorials/packaging-projects/#choosing-a-build-backend
-#
+[build-system]
+# Both of these values will be provided by the documentation for your build backend, 
+# or generated by its command line interface.
 # Usually, you’ll just copy what your build backend’s documentation suggests.
 # There should be no need for you to customize these settings.
-# 
-# If the build-backend parameter is not defined, then the fall-back behaviour 
-# is to use setuptools.
-[build-system]
+#
 # A list of packages that are needed to build your package:
 requires = ["setuptools"]  # REQUIRED if [build-system] table is used
-# The name of the Python object that frontends will use to perform the build:
+# The name of the Python object that frontends will use to perform the build.
+# If not defined, then the fall-back behaviour is to use setuptools.
 build-backend = "setuptools.build_meta"