Fix Table of Contents layout shift

This MR intends to remove Layout Shift from the GitLab Docs caused by Table of Contents (TOC) being redrawn on the client. It does so by placing the server rendered TOC right where the client one should be. It also applies proper styling so it also looks the same.

Before	After
Screen_Recording_2022-02-08_at_12.01.49	Screen_Recording_2022-02-08_at_11.59.29