fix(readme): add imports, remove outdated link, add statement to install dependency

[pichlermarc]

Changes:

• The docs we linked to are down, I removed the link and added info about the necessary imports instead.
• The example was missing instructions to install psutil (when used without a script), so I added a line to do so

[pirgeo]

The OTel versions specified are minimum versions, in the tests, it uses opentelemetry-api and opentelemetry-sdk version 1.16.0 (the latest version). I don't think we need to update any dependency versions.

[pichlermarc]

The OTel versions specified are minimum versions, in the tests, it uses opentelemetry-api and opentelemetry-sdk version 1.16.0 (the latest version). I don't think we need to update any dependency versions.

Yep, the current range picks up 1.16 automatically 🙂