Develop a Google Chrome extension using JavaScript, HTML, and CSS that disables access to social media, online shopping, and other time-wasting websites during work hours (9am-5pm). The extension should have a customizable list of blocked websites and a user-friendly interface. It should also provide the option to whitelist certain websites deemed necessary for work. When a blocked website is attempted to be accessed, the user should be redirected to a custom landing page with motivational quotes or productivity tips. The extension should have a clear on/off switch and be able to run in the background without disrupting other Chrome functions.
This prompt doesn't seem malicious.