Multi 3.0.0

• Added codesign step to app creation, so notifications should work in more scenarios—read the blog post to learn more
• Changed create-mac-app so that omitting MULTI_JSON_CONFIG no longer overwrites an existing JSON config
• Changed Custom CSS/JS injection to happen as early as possible (before document.body is loaded)
• Replaced keepOpenAfterWindowClosed config option with terminateWithLastWindow which defaults to false, matching macOS default behavior
• Removed Better.fyi ad-block list since it is no longer maintained
• Removed "Copy URL" shortcut since it can be implemented with Custom JS