Setting readOnly on Checkbox component should make it read-only.

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

readOnly has no effect

Expected Behavior 🤔

readOnly should make component read-only

Steps to Reproduce 🕹

Working example:
https://codesandbox.io/s/material-demo-sdpbg
Steps:

1. Set readOnly on Checkbox component

Your Environment 🌎