Add a command line tool to generate OAS in a file

aiohttp_pydantic/oas/__main__.py

@@ -0,0 +1,8 @@
+import argparse
+
+from .cmd import setup
+
+parser = argparse.ArgumentParser(description="Generate Open API Specification")
+setup(parser)
+args = parser.parse_args()
+args.func(args)