Adds dummy animation for the root scene node

[onurtore]

🦟 Bug fix

Fixes #393

Summary

Adds dummy animation for the root scene.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[azeey]

@luca-della-vedova would you be able to give this a look?

[luca-della-vedova]

I can't remember the exact details of this PR but iirc it was to fix a corner case when parsing one specific collada actor with the Assimp loader, which in the end is also hidden behind a custom environment variable, we can revisit these corner cases if we were to remove our custom parser and just use assimp for every mesh, otherwise this is extremely niche and not sure about the implications on other models