[Enhancement] Update Stylesheet with fonts used in the project

[thedc89]

To help improve clarity and make the codebase cleaner, all fonts defined in various classes should go to the Stylesheet.swift file.

Example:

titleLabel.font = UIFont(name: "Roboto-Bold", size: UIView.getValueScaledByScreenWidthFor(baseValue: 17))

should be defined in the Stylesheet as follows:

enum FontStyles {
    static let headerTitle = UIFont(name: "Roboto-Bold", size: UIView.getValueScaledByScreenWidthFor(baseValue: 17))
  }