Packagist is the main Composer repository. It aggregates public PHP packages installable with Composer.
Database tools, helpers and related structures.
Application composition structures: layers, exceptions, routing, etc.
Raw HTML composition and management utilities.
Mjolnir compatiblity and legacy support.
Documentation and non-html document support (Markdown, PDFs, etc)
Tooling specific to Mjolnir classes.
Test helpers for Mjolnir.
Theme drivers, Theme composition, Theme management and Mockup helpers.
Mjolnir type information (with Traits).