Describe the bug
When using schematic to generate / update the project, among others, the file spartacus-features.module.ts is generated / updated

Within the spartacus code, this file has the following section:

/************************* Opt-in features *************************/

    ExternalRoutesModule.forRoot(), // to opt-in explicitly, is added by default schematics
    JsonLdBuilderModule,

    /************************* External features *************************/

After running the schematics, the generated file spartacus-features.module.ts in my project does NOT contain the line ExternalRoutesModule.forRoot()

Tell us the version of Spartacus

• Library version: 3.3.0

To Reproduce
Steps to reproduce the behavior:

1. Generate a fresh spartacus project
2. Open the file spartacus-features.module.ts
3. Notice that the file does not contain the ExternalRoutesModule

Expected behavior
According to the comment within the file in the spartacus codebase // to opt-in explicitly, is added by default schematics and since the documentation about the feature does not say anything about opting in manually (https://sap.github.io/spartacus-docs/external-routes/), I would expect, that the schematics adds the line according to the spartacus version of the file spartacus-features.module.ts.

Screenshots
Spartacus Feature Module:

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Other Ticket about External Routing
#12292