New creates a new manifest with the Environments intialized.

DefaultEnvironmentName is the name invoked from draft.toml on `draft up` when --environment is not supplied.

DefaultNamespace specifies the namespace apps should be deployed to by default.

DefaultWatchDelaySeconds is the time delay between files being changed and when a new draft up` invocation is called when --watch is supplied.

Environment represents the environment for a given app at build time.

Manifest represents a draft.toml.