Programatic themes

[rivera-ernesto]

With this changes it is now possible both to create Theme objects fully programmatically, or also adjust themes read from json files.

Sample fully programatic theme that handles iOS 13 dark mode:

var theme = Theme()
theme.body.attributes = [.font :  UIFont.inter(), .foregroundColor : UIColor.secondaryLabel]
theme.styles.append(Style(element: .h1, attributes: [.font : UIFont.inter(size: 24), .foregroundColor : UIColor.label]))
theme.styles.append(Style(element: .h2, attributes: [.font : UIFont.inter(size: 18), .foregroundColor : UIColor.label]))
theme.styles.append(Style(element: .h3, attributes: [.font : UIFont.inter(size: 16), .foregroundColor : UIColor.label]))
theme.styles.append(Style(element: .bold, attributes: [.font : UIFont.inter(weight: .bold)]))
theme.styles.append(Style(element: .italic, attributes: [.font : UIFont.inter(italic: true)]))
theme.styles.append(Style(element: .boldItalic, attributes: [.font : UIFont.inter(weight: .bold, italic: true)]))
theme.styles.append(Style(element: .code, attributes: [.font : UIFont(name: "CourierNewPSMT", size: 15)!, .foregroundColor : UIColor.label, .backgroundColor : UIColor.secondarySystemBackground]))
theme.styles.append(Style(element: .image, attributes: [.foregroundColor : UIColor.appTint]))
theme.styles.append(Style(element: .url, attributes: [.foregroundColor : UIColor.appTint]))

[ruddfawcett]

Looks great — thanks again @rivera-ernesto. 🎉