Add DeepPane focus workspace extension

[AntMesh]

Summary

• Adds DeepPane to the General section.
• Links directly to the live Chrome Web Store listing.
• Uses a concise description of the extension's implemented focus-workspace features.

Disclosure

I maintain DeepPane and am submitting our own extension for consideration. Version 0.1.6 is publicly listed on the Chrome Web Store as of July 19, 2026.

Contribution checks

• Read and followed contributing.md.
• Confirmed DeepPane is not already listed.
• Added one extension in the required [Name](link) - Description. format.
• Description starts with a capital letter and ends with a period.