add `author` and `contributors` field to package.json
add `author` and `contributors` field to package.json

MichaelFBA/gulp-minify-css,LoicMahieu/gulp-minify-css,keremciu/gulp-minify-css,zarko-tg/gulp-minify-css,HaNdTriX/gulp-minify-css,sibrus/gulp-minify-css