An add-on uses a manifest file to configure certain details about the app and its operation.
This documentation covers the details of configuring a manifest for a Editor Add-on.
Manifest structure for Editor Add-ons
The Apps Script manifest structure doesn't include any properties that are specific to Editor Add-ons. However, Editor Add-on manifests can define the general properties that are common to all Apps Script projects, such as OAuth scopes and library dependencies.
See Manifest structure for a full list of potential manifest properties that Editor Add-ons can use.