Integration tests and examples: Tensorflow

[cosmicBboy]

• extend the integration test suite to include a tensorflow-based app: https://github.com/unionai-oss/unionml/tree/main/tests/integration
• update the documentation index.md to include a new tensorflow tab: https://github.com/unionai-oss/unionml/blob/main/docs/source/index.md

[shivaylamba]

#self-assign

[Smartmind12]

@cosmicBboy can i work on this as a part of hacktoberfest??

[Smartmind12]

#self-assign