Bump chart.js from 2.7.3 to 2.8.0

Bumps [chart.js](https://github.com/chartjs/Chart.js) from 2.7.3 to 2.8.0.
- [Release notes](https://github.com/chartjs/Chart.js/releases)
- [Commits](https://github.com/chartjs/Chart.js/compare/v2.7.3...v2.8.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -14,7 +14,7 @@
     "autosize": "^3.0.20",
     "axios": "^0.18",
     "bootstrap-sass": "^3.4.1",
-    "chart.js": "^2.7.0",
+    "chart.js": "^2.8.0",
     "cross-env": "^5.1",
     "es5-shim": "^4.5.9",
     "flatpickr": "^4.5.7",