feat: some updates to #92

[SgtPooki]

minor code cleanup and improvements for #92

• chore: PR comments and minor improvements
• fix: use sw-cache-expires
• chore: cleanup hasExpired return
• chore: log on cache miss
• chore: wait for response so we can cache it
• chore: minor cleanup
• chore: minor cleanup
• fix: stale-while-revalidate for ipns

notable changes:

1. stale-while-revalidate only for IPNS content (if people want no network requests, query ipfs resource)
2. sw-cache-expires as called out by @2color
3. consolidation of fetch + update cache in fetchAndUpdateCache function

[2color]

Very nice! Thanks for the polish