Feature more prominently how to enable OpenTelemetry instrumentation

[nikolaydubina]

#3205

This is based on discussion regarding that OpenTelemetry instrumentation for redis is does note show up in Google Search or in docs easily enough, so people may not find it (even though it is awesome and exists!). Let's give it more spotlight!

1. hopefully people more likely to see this while browsing GitHub and pkg.go.dev
2. hopefully Google will index keywords "OpenTelemetry", "Instrument", "Trace" while crawling README.md next time

[nikolaydubina]

cc: @ndyakov

[ndyakov]

Thank you, @nikolaydubina! Would you mind adding OpenTelementry to the wordlist.txt so the spellcheck passes.

[nikolaydubina]

ok, done