[NUI] Add Strikethrough Property (#3844)

[NUI] Add Strikethrough Property (#3844)

Add Strikethrough Set/Get methods to NUI
Strikethrough is a typographical presentation of words with a horizontal line through their center

The strikethrough map contains the following keys:

    enable (bool): Whether the strikethrough is enabled (the default value is false)
    color (Color): The color of the strikethrough (If not provided then the color of the text is used)
    height (float): The height in pixels of the strikethrough (the default value is 1.f)

Added:

    public void SetStrikethrough(Strikethrough strikethrough) // Method to TextLabel, TextEditor & TextField
    public Strikethrough GetStrikethrough() // Method to TextLabel, TextEditor & TextField

Related patches on DALi:

    Add Strikethrough Property : https://review.tizen.org/gerrit/c/platform/core/uifw/dali-csharp-binder/+/263388
    Extending Style - Adding Strikethrough : https://review.tizen.org/gerrit/c/platform/core/uifw/dali-toolkit/+/258031