[Enhancement]: Use fiber.Map instead of map object

[NimishKashyap]

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

Problem/Feature

GoFiber package recommends using fiber.Map{} type which is an alias of map interface for easier JSON handling.

Description of Changes:

• Changed map[string]string type for HelloWorldHandler response to standard fiber.Map{} as recommended by the package.

Checklist

• I have self-reviewed the changes being requested
• I have updated the documentation (if applicable)

[Melkeydev]

LGTM