Feature: PWA

**Which module(s) and week(s) does this change affect?**

**What is the work that needs to be done?**

Write a serviceworker that precaches urls
And a proper manifest
To make the site available offline and as a pinned app offline

**Why is this work important to do?**

We need to make our site as available as possible to our users
Many of our users have restricted data and choppy access
Caching our entire site (within reason, limiting images and no videos) is about 20mb? That's about 20 minutes of browsing time on average
I would probably just forward cache a subset - prep, day-plan, backlogs, and guides? Probably 7- 12mb

**Additional context**

**Who might need to know about this change?**