iLockIt от coolbit

For contribution: https://github.com/iamneek/iLockIt

For getting to options (navigate to github link above for screenshots on how to do it):
Step 1: Go to extensions page
Step 2: Click on the three dots beside the iLockIt extension
Step 3: Click on Options

Features

• Lock any domain or wildcard subdomains (for example, example.com or *.news.com)
• Password-protected access to locked sites
• Suspension timer options: immediately, 2, 5, 10, 30 minutes, or custom
• Options page to manage locked sites and password
• Optional masking of toolbar icon and title