refactor to return / store IDecorations
refactor to return / store IDecorations

Tyriar/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js,Tyriar/xterm.js,Tyriar/xterm.js,xtermjs/xterm.js,xtermjs/xterm.js