Added status error codes to responses

[sohammk08]

High Level Overview of Change

Added status error codes to responses

Context of Change

Addresses #66

Type of Change

• [x] New feature (non-breaking change which adds functionality)

Before / After

Changed these two lines so that they provide appropriate status error codes:

233:   if (validator === undefined) {
234:     res.status(404).json({ result: 'error', message: 'Validator not found' })
235:      return
236:    }

275:  } catch {
276:    res.status(500).json({ result: 'error', message: 'Internal server error' })
277:  }