Added licence.md
Added licence.md

Closes #9.

wieslawsoltes/Perspex,punker76/Perspex,susloparovdenis/Perspex,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,akrisiun/Perspex,OronDF343/Avalonia,sagamors/Perspex,grokys/Perspex,SuperJMN/Avalonia,susloparovdenis/Perspex,jkoritzinsky/Avalonia,jazzay/Perspex,MrDaedra/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,kekekeks/Perspex,tshcherban/Perspex,jkoritzinsky/Perspex,grokys/Perspex,jkoritzinsky/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,susloparovdenis/Avalonia,Perspex/Perspex,kekekeks/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,OronDF343/Avalonia,danwalmsley/Perspex,jkoritzinsky/Avalonia,DavidKarlas/Perspex,susloparovdenis/Avalonia,ncarrillo/Perspex,wieslawsoltes/Perspex,wieslawsoltes/Perspex,MrDaedra/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,Perspex/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,bbqchickenrobot/Perspex