Added missing doc comments.
Added missing doc comments.

jkoritzinsky/Avalonia,MrDaedra/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,wieslawsoltes/Perspex,grokys/Perspex,wieslawsoltes/Perspex,wieslawsoltes/Perspex,MrDaedra/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,akrisiun/Perspex,jkoritzinsky/Perspex,SuperJMN/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,Perspex/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,jkoritzinsky/Avalonia,Perspex/Perspex,SuperJMN/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,jazzay/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia