mixin for easier @media use

media.less

@maxlg: ~"(max-width: 1199px)";
@maxmd: ~"(max-width: 991px)";
@maxsm: ~"(max-width: 767px)";
@maxxs: ~"(max-width: 320px)";
@minlg: ~"(min-width: 1200px)";
@minmd: ~"(min-width: 992px)";
@minsm: ~"(min-width: 768px)";
@mdtolg: ~"(min-width: 992px) and (max-width: 1199px)";
@smtomd: ~"(min-width: 768px) and (max-width: 991px)";
@smtolg: ~"(min-width: 768px) and (max-width: 1199px)";
@xstosm: ~"(min-width: 321px) and (max-width: 767px)";
@xstomd: ~"(min-width: 321px) and (max-width: 991px)";
@xstolg: ~"(min-width: 321px) and (max-width: 1199px)";

// @media @maxxs {
//     param: val;
// }