Add Loading Icon to Table of Content

Description: Add a loading icon to the table of contents in collection pages, much like what was done in #5 (closed). See Image 97.1 for details.

Documentation (More Info): https://docs.google.com/document/d/1PwckT4g9LPnVnVC1edQzxYxN85BL5wot522-YqgEOSA/edit?usp=sharing