✨ v3 (feature): use any as default Message type of Error struct

[efectn]

closes #1825

[harryrford]

On a side note for the v3 fiber Error type shouldn't we include a method added to the Ctx such as ctx.SendError(err Error) to encourage usage of the type (as an exported package defined variable) and avoid writing helpers such as:

func SendError(c *fiber.Ctx, code int, message string) error {
	c.Status(code)
	return c.JSON(fiber.NewError(code, message))
}

Instead a method could simply be defined as:

func (c *Ctx) SendError(err Error) error {
	c.Status(err.Code)
	return c.JSON(err)
}

[efectn]

On a side note for the v3 fiber Error type shouldn't we include a method added to the Ctx such as ctx.SendError(err Error) to encourage usage of the type (as an exported package defined variable) and avoid writing helpers such as:

func SendError(c *fiber.Ctx, code int, message string) error {
	c.Status(code)
	return c.JSON(fiber.NewError(code, message))
}

Instead a method could simply be defined as:

func (c *Ctx) SendError(err Error) error {
	c.Status(err.Code)
	return c.JSON(err)
}

I don't think it's good idea to add SendError method into the context. Because some people may want to just send error message instead of Error struct. It's very specific. Probably this PR will be helpful for your use case: #1928