Add contact information for OpenAPI generation

[lnash94]

Description:
Introduced email, and description fields to the openapi ServiceInformation for capturing the contact information in the generated directory.

public type ServiceInformation record {|
    ...
    string email?;
    string description?;
|};

openapi: 3.0.1
info:
...
  description: "This service provides the capabilities to convert an amount from one currency to one to many different currencies."
  contact:
    email: "sumudu@abc.com"

[lnash94]

Close with the favour of ballerina-platform/openapi-tools#1731