Apply suggestions from code review

Co-authored-by: Randy Döring <[email protected]>

docs/building-extension-modules.md

@@ -26,12 +26,12 @@ In order to achieve this, at the highest level, the following steps are required
 {{< step >}}
 **Add Build Dependencies**
 
-The build dependencies, in this context, refer to those Python packages that required in order to successfully execute
+The build dependencies, in this context, refer to those Python packages that are required in order to successfully execute
 your build script. Common examples include `cython`, `meson`, `maturin`, `setuptools` etc., depending on how your
 extension is built.
 
 {{% note %}}
-You must assume that only python built-ins are available by default in a build environment. This means, if you use need
+You must assume that only Python built-ins are available by default in a build environment. This means, if you need
 even packages like `setuptools`, it must be explicitly declared.
 {{% /note %}}
 
@@ -57,7 +57,7 @@ poetry add --group=build setuptools cython
 {{< step >}}
 **Add Build Script**
 
-The build script can be free-form Python script that uses any dependency specified in the previous step. This can be
+The build script can be a free-form Python script that uses any dependency specified in the previous step. This can be
 named as needed, but **must** be located within the project root directory (or a subdirectory) and also **must**
 be included in your source distribution. You can see the [example snippets section]({{< relref "#example-snippets" >}})
 for inspiration.
@@ -122,7 +122,7 @@ documentation for information on each of the relevant sections.
 script = "build-extension.py"
 
 [build-system]
-requires = ["poetry-core", "cython"]
+requires = ["poetry-core", "cython", "setuptools"]
 build-backend = "poetry.core.masonry.api"
 ```