docs: Add sample inference requests (#184)

#### Motivation

To users, it's not clear how to send inference requests to many of the the provided sample models
in our minio image. 

#### Modifications

In the example models doc, corresponding example inference requests using grpcurl were added.

#### Result

Clearer insight into sending inference requests to sample models.

Closes: #165 


Signed-off-by: Paul Van Eck <[email protected]>