Add warning about precision in interfaces documentation

[justinpickering]

Context:
A user query on our forum (Thread #8885) revealed that PennyLane silently promotes all float32 inputs to float64 during computation.

Description of the Change:

This change adds a warning to the Interfaces documentation regarding the behaviour (everything is promoted to 64-bit outputs).

Benefits:

Possible Drawbacks:

Related GitHub Issues:

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.40%. Comparing base (0c99124) to head (aec8aae).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8124      +/-   ##
==========================================
- Coverage   99.40%   99.40%   -0.01%     
==========================================
  Files         550      550              
  Lines       56969    56969              
==========================================
- Hits        56631    56630       -1     
- Misses        338      339       +1     

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[CatalinaAlbornoz]

Thanks for adding this warning! 🙌
The line was a bit long so I just suggested making it into two lines.
Remember to add an entry to the changelog in the "documentation" section.

[justinpickering]

Thanks for adding this warning! 🙌 The line was a bit long so I just suggested making it into two lines. Remember to add an entry to the changelog in the "documentation" section.

Added - thanks @CatalinaAlbornoz!

[CatalinaAlbornoz]

LGTM!