add node env to eslint config file
add node env to eslint config file

prevent 'require' is not defined error in gulpfile.js

vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle.js,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle-ui,vivliostyle/vivliostyle.js