Create GET /api/voters

[shuse2]

Description

• Add /api/voters which returns the below JSON:

[{
  address: '',
  username: '',
  totalVotesReceived: '',
  voters: [{ address: '', amount: '' }],
}]

Motivation

The forging helper should return the votes each delegate received.

Acceptance Criteria

• Add unit test to check if the return value is as described above
• Check if the response is return as expected by registering to the framework

Additional Information

Related issues: #5215