Rated 1 out of 5 stars

Oh, so you re-invented the bicycle...
This all already exists in Firefox. This function is called "list all tabs" with gets turned on by about:config pref browser.allTabs.previews set to true.
All the difference is that:
1. your extension opens this preview in the new tab, not above the existing one. It's actually a bad idea.
2. you've added a hotkey. This can be done using other extensions too.

You'd better spend your time at creating something that was not already done before.
If you don't know what to do - I can give you some ideas.