[docs] contribute opentelemetry.io docs updates for SDK 2.0

[pichlermarc]

Description

Important

only start working on this once we get close to release to avoid churn and spamming opentelemetry.io with PRs that are not yet actionable.

Once we have a releasable state of the 2.0 SDK, we should also update documentation on opentelemetry.io (prepare PRs and get them to a mergeable state before actual release) to ensure new users don't run into problems with outdated documentation.

This issue is considered done when:

• pull requests updating opentelemetry.io docs have been submitted
• pull requests for opentelemetry.io are in a mergeable state