fix url-regex vulnerability

[SimonDeRidder]

When installing via npm, a warning is issued:
┌──────────┬─────────────────────────────┐
│ High │ Regular Expression Denial of Service │
├──────────┼─────────────────────────────┤
│ Package │ url-regex │
├──────────┼─────────────────────────────┤
│ Patched in │ No patch available │
├──────────┼─────────────────────────────┤
│ Dependency of │ gulp-concat-css [dev] │
├──────────┼─────────────────────────────┤
│ Path │ gulp-concat-css > rework-import > url-regex │
├──────────┼─────────────────────────────┤
│ More info │ https://npmjs.com/advisories/1550 │
└──────────┴─────────────────────────────┘
More info in kevva/url-regex#70
It seems the issue can be fixed by switching to https://github.com/niftylettuce/url-regex-safe

[retroburst]

Also would really like to see this fixed as well!

[mattiaskagstrom]

Related: reworkcss/rework-import#20