add comments and docs to sw.js,

add service worker ADR

specs/adrs/120222-serviceworker-netfirst.md

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+# Use a network first cache second for service worker architecture 
+
+- Status: in consideration
+- Deciders: Arthur Lu
+- Date: 12 / 02 / 22
+
+## Decision Drivers
+
+- Need to balance the need for user ease of use and local first priority
+- Users should expect to update their app easily when they have network, but may not be expected to know how to perform a hard refresh
+- Local first priority means we should avoid unnecessary network activity when possible
+
+## Considered Options
+- Network first cache second
+- Cache first network second
+
+## Decision Outcome
+
+Chosen Option: TBD