Add a mkdocs extension to generate the --help output (#720)

* Add a mkdocs extension to generate the --help output

* Add the correct setuptools syntax for relative requirements

* docs: use macro plugin instead

* docs: remove indirection in docs

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>

docs/main.py

@@ -0,0 +1,13 @@
+import subprocess
+from typing import Any
+
+# Requires Python 3.7+
+
+
+def define_env(env: Any) -> None:
+    "Hook function for mkdocs-macros"
+
+    @env.macro
+    def subprocess_run(*args: str) -> str:
+        "Run a subprocess and return the stdout"
+        return subprocess.run(args, check=True, capture_output=True, text=True).stdout