Add gifs for baseline agent in benchmark scenarios

[Adaickalavan]

• Gifs show a trained baseline agent attempting the Driving SMARTS 2023.1, 2023.2, and 2023.3, benchmark training scenarios.
• Gifs are hosted at https://github.com/smarts-project/smarts-project.github.io
• See the following for sample of built pages incorporating the new gifs.
  • https://smarts.readthedocs.io/en/zoo-8/benchmarks/driving_smarts_2023_1.html#training-scenarios
  • https://smarts.readthedocs.io/en/zoo-8/benchmarks/driving_smarts_2023_3.html#training-scenarios