feat: grpc integration

[nully0x]

This PR implements grpc server calls for fresheye's network calls and exposes it to FE clients for interaction.

Todo:

• [x] complete integration of all methods and functions from the initial lib
• [x] documentation of grpc calls

To setup locally:

• copy and update the values in the .env example to your details. Mostly github_token which you can get from your github developer portal.
• in the root folder, run make run-grpc this starts the server on port 50051 and it is ready to accept grpc calls.
• currently, the major implementation to create PR is process_pull_request which runs all the jobs to fork and create a PR on the operator's GitHub account. By design, this will be on fresheyes repo later.
• as it is a grpc server, the proto file is in the root directory which you can use to generate schema for the client also.
• An example of a sample call via Postman is attached.

[nully0x]

@Extheoisah please review and test.