Describe the bug
In a single or two-column layout, if you try opening and navigating through your sidebar menu (index, drafts, etc) using Tab key you can't focus on the menu itself so the focus stays in the email list even though the sidebar is open and blocking the view.

To Reproduce
Steps to reproduce the behavior:

1. Go to the mail list (or any other page) while in a single or two-column layout
2. Press Tab until you highlight the hamburger menu icon and press Enter
3. Try tabbing two navigate between the menu options.

Expected behavior
Navigate through the menu options

Test Notes

• On single and two-columns layout, when opening sidebar through hamburg menu, we should be able to tab inside it.
• Tabbing anywhere else on the application should not be allowed while the sidebar is open.