feat: OpenTelemetry support

[bitttttten]

Brief Description of the Bug

Is there a plan to add OpenTelemetry support? It would be really valueable for us to how the cache handler plays into our full flow of queries.

Severity
Cosmetic/Minor

Frequency of Occurrence
Always

Steps to Reproduce
It's not a bug.

Screenshots/Logs

For example, here is a screenshot from our otel application. It contains a lot of fetches, although we don't know which ones are these are from our cache-handler. We don't know which ones are being intercepted by the nextjs fetch handler since nextjs takes over fetch.

[better-salmon]

@bitttttten hey there! CacheHandler operates in a separate thread, which means it can't access the instrumentation provided by open telemetry users. I'm currently focusing on a big feature for the library. Perhaps once that's done, I'll be able to allocate time to incorporating open telemetry support.