autopep8: add README (#7249)

plugins/autopep8/README.md

@@ -0,0 +1,8 @@
+# autopep8 plugin
+
+This plugin adds completion for [autopep8](https://pypi.org/project/autopep8/), a tool that automatically formats Python code to conform to the [PEP 8](http://www.python.org/dev/peps/pep-0008/) style guide.
+
+To use it, add autopep8 to the plugins array of your zshrc file:
+```
+plugins=(... autopep8)
+```