RAT reports Unknown license for new .js files

[dangogh]

the trafficcontrol-rat Jenkins job is reporting this:

Files with unapproved licenses:

  apache-trafficcontrol-3.0.0/traffic_portal/app/src/assets/js/chartjs/Chart.min_2.7.2.js
  apache-trafficcontrol-3.0.0/traffic_portal/app/src/assets/js/chartjs/angular-chart.min_1.1.1.js

The files are properly licensed, but need to be added to .rat-excludes so rat doesn't report this.

[dangogh]

@chadgilloth ^^