Service worker offline cache not working

[johncalvinroberts]

The service worker is either not properly caching assets, or not properly retrieving cached assets when offline.

Expected Behavior

When network is not available, the service worker should check the manifest-1.0.0 appcache for an asset, and serve it from the cache if a match is found.

Original task -- #22, implementation in #69

Current Behavior

When network is not available, the app does not load.

Possible Solution

Pretty sure I have the solution, it's just a missing return value on one of the SW hooks -- will open PR momentarily.

Edit: #143

Steps to Reproduce (for bugs)

1. Either run the prod build on local env or visit the production app -> https://www.manifest.app/
2. If in chrome, open devtools -> application tab -> cache storage -> manifest-1.0.0 -- confirm assets are being cached
3. Either turn wifi off on your machine, or set throttling to offline in chrome dev tools
4. Refresh the page
5. Confirm -- page does not load

Context

I'm working on a similar lightweight utility app, and I checked out the Service Worker implementation on manifest as a reference. Super sick app by the way, huge inspiration!

[jonathontoon]

Merged. Thanks again for the fix @johncalvinroberts.