[Markdown] Fix regex for URL parsing.
[Markdown] Fix regex for URL parsing.

hwthomas/xwt,directhex/xwt,iainx/xwt,steffenWi/xwt,mminns/xwt,hamekoz/xwt,mminns/xwt,cra0zy/xwt,mono/xwt,antmicro/xwt,akrisiun/xwt,TheBrainTech/xwt,sevoku/xwt,lytico/xwt,residuum/xwt