add new description field

[mishmanners]

This pull request includes changes to the pet class in the src/backend/petspotr.py file. The most important changes include adding a new attribute to the pet class, introducing new methods, and updating the constructor to accommodate the new attribute.

Updates to the pet class:

• Added a new attribute Description to the pet class and updated the constructor to initialize it. (src/backend/petspotr.py)
• Introduced a new method predict_image to the pet class. (src/backend/petspotr.py)
• Introduced a new method alert_owner to the pet class, which takes a DaprClient object as a parameter. (src/backend/petspotr.py)