Add multiline and browser hacks tests for property-no-unknown
Add multiline and browser hacks tests for property-no-unknown

stylelint/stylelint,gucong3000/stylelint,gaidarenko/stylelint,gucong3000/stylelint,gaidarenko/stylelint,hudochenkov/stylelint,stylelint/stylelint,hudochenkov/stylelint,gucong3000/stylelint,gaidarenko/stylelint,hudochenkov/stylelint,stylelint/stylelint,heatwaveo8/stylelint,heatwaveo8/stylelint,heatwaveo8/stylelint,stylelint/stylelint