Adding examples and modifying grpc to add interceptor for streaming

[coolwednesday]

• This PR adds examples for the current gofr-cli approach to additionally also let user generate gRPC streaming handlers with all the observability features, i.e. logs, metrics, traces.
• This PR can only be merged after merging CLI PR : Adding template to generate grpc streaming code gofr-cli#48
• gRPC Streaming on the server side can be of three types. Below are the screenshots of a running streaming gRPC Server (added in the example) with all three types of methods defined on it :
  Logs :

**Metrics :** **Traces:**

- Server Side Streaming

- Client Side Streaming

- Bi-directional Streaming