Feature: Text style

[prochazkafilip]

Overview:
This pull request adds a new structure, TextStyle, to the codebase, which provides a comprehensive way to define and apply text styles in SwiftUI applications. The TextStyle structure allows developers to specify various attributes such as font type, size, line height, font scaling, letter spacing, text case, and text decoration. The primary goal of this enhancement is to simplify the process of translating text styles from Figma designs into SwiftUI, ensuring consistency and ease of use.

Usage:
Developers can apply the text style to views using the textStyle(_:) modifier or specifically to Text views with the textStyleText(_:) modifier. The stylize(with:) method allows applying the text style to attributed strings, and an initializer for NSAttributedString simplifies the creation of attributed strings with the specified text style.

Example:

extension TextStyle {
    static let title = TextStyle(
        fontType: .system(weight: .bold),
        size: 24,
        lineHeight: 32,
        scaling: .relativeTo(textStyle: .title),
        letter: .relative(percent: 5),
        textCase: .uppercase,
        textDecoration: .underline
    )
}

struct ExampleView: View {
    var body: some View {
        Text("Title")
            .textStyle(.title)
    }
}

Notes:

The textStyleText(_:) modifier and the stylize(with:) method do not apply line spacing, text case, or vertical padding based on line height.
This enhancement aims to streamline the integration of text styles from Figma designs into the SwiftUI framework, improving code maintainability and visual consistency across the application.