Minor CONTRIBUTING.md improvements

Author: honno

CONTRIBUTING.md

@@ -2,9 +2,6 @@
 
 Thank you for your interest in contributing!
 
-
-## Contributing
-
 If you would like to contribute textual clarifications or other "maintenance
 type" changes, please open a pull request on the
 https://github.com/data-apis/array-api repository.
@@ -22,15 +19,21 @@ opening an issue for discussion may be more appropriate as a first step.
 The spec website comprises of multiple Sphinx docs (one for each spec version),
 all of which exist in `spec/` and rely on the modules found in `src/` (most
 notably `array_api_stubs`). To install these modules and the additional
-dependencies of the Sphinx docs, you can use:
+dependencies of the Sphinx docs, you can use
 
 ```sh
 $ pip install -e .[doc]  # ensure you install the dependencies extra "doc"
 ```
 
 To build specific versions of the spec, run `sphinx-build` on the respective
-folder in `spec/`. To build the whole website, which includes every version of
-the spec, you can utilize the `make` commands defined in `spec/Makefile`:
+folder in `spec/`, e.g.
+
+```sh
+$ sphinx-build spec/draft/ _site/draft/
+```
+
+To build the whole website, which includes every version of
+the spec, you can utilize the `make` commands defined in `spec/Makefile`, e.g.
 
 ```sh
 $ make