WIP Service-worker documentation

[that-jill]

Checklist:

• I have performed a self-review of my own code,
• I have commented my code, particularly in hard-to-understand areas,
• I have made corresponding changes to the documentation,
• I have added tests that prove my fix is effective or that my feature works,
• New and existing unit tests pass locally with my changes ("bundle exec rake"),
• Title include "WIP" if work is in progress.

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Resolves #1

Description

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not
  work as expected)
• This change requires a documentation update
• Documentation update

How Has This Been Tested?

Screenshots

[LizPrescott]

hi @that-jill and @cflipse does this need anything to get it across the finish line? I see it's approved for merge but still marked wip? Anything I can do to help?