Feature: Diffshub: Pin files to keep them visible while reviewing other files

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

Add right drawer or floating pannel with pinned files while reviewing the other files.

Motivation and context

While reviewing large migrations, most of the times I want to look to two unrelated files at same time to compare each other.

Today I just open a new tab but would be nice to have that natively by just clicking in the file and making it float or opened as right drawer to allow me review the other files while I can read that specific file at same time.