vendor.yml: improved & added more regex for stylesheets from third party

Many repos (especially Meteor repos) are being mistakenly marked as CSS due to innumerable lines of supposedly excluded auto-generated CSS code not being excluded from statistics.
Here are some examples:
https://github.com/Differential/meteor-boilerplate
https://github.com/Urigo/angular-meteor
https://github.com/yogiben/meteor-starter
https://github.com/0a-/0a.io