feat: Now allowing users to use Gemini in addition to OpenAI

[iSparsh]

Changelog

This addresses #15

• Removed hardcoded OpenAI references
• Added a new LLM Interface files to easily add new LLM providers in the future, giving a standard way to access their functionality by implementing dependency injection
• Added front-end changes to choose providers and available models, which selects the appropriate provider in the backend and functions correctly
• Tested the new LLM interface to see if it switches to correct provider based on selected request ✅
• Tested functionality using user-experience tests (on localhost) ✅
• Added a .gitignore file to remove common developer directories generated in a developer environment

Future functionality to be developed

1. Spelled-out developer documentation for old and newly added features
2. Switching to other front-end, as based on fronted #12

Please let me know if any changes need to be made, or any documentation provided!

[AdiistheGoat]

Thanks for the contribution bro.

Comments:

• Why is the code only specific to gemini and openai..I though it was an LLM interface..
• Can you pls provide class comments (refer to what I did) for the added code
• Pls don't upload your .gitignore to GitHub. It should only be on your local

Other comments:

• Next time, can you pls have multiple commits. Your PR has only 1 commit which is not good practise.

It looks really good overall! Can u test it much more locally (don't worry about the open ai api costs) and make the changes I suggested. Thanks!

[iSparsh]

As per our discussions,

• I have added class comments in your required format.
• I have kept the .gitignore to include common development directory
• Tested production enviroments to ensure Gemini models and OpenAI models work

Additionally, again as we discussed, I would like to add unit and integration tests, and also use GitHub Actions to make the CI/CD pipeline more streamlined to traditional practices. We can do that in another PR and keep track of it in another issue.

Please review the changes, thanks!