[Data] Fetch feed from API

[johnGachihi]

Scope

Add feed API client.

Note

• Assumes the created_at field in the API response is in our timezone. (I suggest that it be in ISO 8601 format with time zone info)
• Added desugaring to allow using java.time classes

Question

• How will paging be implemented? And is that in the scope of this task?

Please make sure to read https://github.com/droidconKE/droidconKE2022Android/docs/CONTRIBUTING.md and check that you understand and have followed it as best as possible Explain what your feature does in a short paragraph. please check the below boxes

• [ ] I have followed the coding conventions
• [x] I have added/updated necessary tests
• [ ] I have tested the changes added on a physical device
• [x] I have run ./codeAnalysis.sh to make sure all lint/formatting checks have been done.

[misshannah]

Hi @johnGachihi, please pull from the main branch then commit so that we can approve this PR well.