Add release cadence (#880)
Add release cadence (#880)

* add note about monthly cadence

Update the release section of the readme to include the monthly cadence of releases.

Fixes #457

* add note about monthly cadence

Update the release section of the readme to include the monthly cadence of releases.

Fixes #457
open-telemetry/opentelemetry-python-contrib,open-telemetry/opentelemetry-python-contrib,open-telemetry/opentelemetry-python-contrib