Add ember-source v5 to peers list

[NullVoxPopuli]

This polyfill does nothing after 4.1, https://github.com/ember-polyfills/ember-cached-decorator-polyfill/blob/main/lib/transpile-modules.ts#L19

But folks may be using it for typescript reasons. (esp if they aren't using the built-in types yet)

This PR eliminates a peer warning / violation from @ember-data/model in default app creation:

├─┬ ember-data 5.0.0
│ └─┬ @ember-data/model 5.0.0
│   └─┬ ember-cached-decorator-polyfill 1.0.1
│     └── ✕ unmet peer ember-source@"^3.13.0 || ^4.0.0": found 5.0.0

[NullVoxPopuli]

bah, needs an upkeep PR first

[jrjohnson]

This is a harder break today with Embroider v3.2.0. Now dying with:

Some V1 ember addons are resolving as incorrect peer dependencies. This makes it impossible for us to safely convert them to v2 format.
See https://github.com/embroider-build/embroider/blob/main/docs/peer-dependency-resolution-issues.md for an explanation of the problem and suggestions for fixing it.

dummy@0.0.0 (dev)-> ember-data@4.12.3 -> @ember-data/model@4.12.3 -> ember-cached-decorator-polyfill@1.0.1
    sees peerDep ember-source@4.12.3

[NullVoxPopuli]

I don't have npm access for publishing (it seems all of CI is failing due to TS issues with @ember/test-helpers tho... I wonder if that's important or just "dummy app" stuff).

@simonihmig has npm access :upside_down_face:

[simonihmig]

Ci seems to be failing with floating deps due to something pulling in @ember/test-helpers v3, which needs node 16+, but we still have 14 here. We should drop node 14. Anyway, I'll go ahead and merge this, and publish a bit later from my private machine! :)

[jrjohnson]

Thanks!