chore: Design settings level vertical tabs based on wireframes

[mikejhale]

Design third level vertical setings based on wireframes provided by @mehul0810 for #4204

[DevinWalker]

Third-level Navigational Settings Tabs

@mehul0810 here's the concept I have for the third-level tabs:

Functional Notes

1. The tabs change on click (no page reload required)
2. Because they change on the fly the top level menu only goes to the Stripe base root.
3. The first tab's title and the first setting should align horizontally
4. I changed "Stripe Settings" to just "Stripe"1
5. The main tab is bold and the unselected tabs are semi-bold
6. Note the subtle box shadow on the container. We should make that reusable in sass for other containers.

If you have any questions, let me know. If you like them and can proceed, then please close the issue.

[mikejhale]

Closing as development work has begun on third level settings tabs.