doc: Add EIRP and ERP

[pradeeka7]

Summary

Add EIRP and ERP to the learn section. This tutorial is written for the things advanced certification.

Screenshots

Changes

• Created a new page for EIRP and ERP
• ...

Notes for Reviewers

Checklist

• [X] Scope: The referenced issue is addressed, there are no unrelated changes.
• [X] Run Locally: Verified that the docs build using make server, posted screenshots, verified external links.
• [X] Style Guidelines: Documentation obeys style guidelines in CONTRIBUTING.
• [X] Commits: Commit messages follow guidelines in CONTRIBUTING, there are no fixup commits left.