Add git-absorb and shell-history-per-project (baxyz)

[baxyz]

What type of PR is this?

• Add a new dev container collection
• Update to an existing dev container collection
• Documentation/spec update
• Other containers.dev site update (UX, layout, etc)

Related Issues

• No Related Issue
• No Closes

Description

This PR adds two new dev-container features from the baxyz collection to the index:

1. Git Absorb Feature - A feature that provides git-absorb, a tool for automatically absorbing fixup commits into their target commits
2. Shell History Per Project Feature - A feature that maintains separate shell command history for each project/workspace

Both features are available at: https://github.com/baxyz/devcontainer-features/

Collection checklist

If your PR contributes a new collection, please utilize this checklist:

• Collection name
• Maintainer name
• Maintainer contact link (i.e. link to a GitHub repo, email)
• Repository URL
• OCI Reference
• I acknowledge that this collection provides new functionality, distinct from the existing collections part of this index.