The $AliasPlugin is what powers the aliases feature of Mosaic.

It does this by scrapes aliases from page metadata and also applies all aliases stored in config.data.aliases

Other plugins can use setAliases to apply new aliases, as long as they call it before this plugin has reaches the $beforeSend lifecycle event.

This plugin is added to the plugins collection by Mosaic itself so users do not need to include it in their own mosaic config file.

This plugin runs with a priority of -1 so it runs after most other plugins.