Bump chart.js from 2.8.0 to 2.9.4

Bumps [chart.js](https://github.com/chartjs/Chart.js) from 2.8.0 to 2.9.4.
- [Release notes](https://github.com/chartjs/Chart.js/releases)
- [Commits](chartjs/Chart.js@v2.8.0...v2.9.4)

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

Author: dependabot[bot]

package-lock.json

@@ -11,7 +11,7 @@
   "dependencies": {
     "axios": "^0.19.2",
     "buefy": "^0.8.3",
-    "chart.js": "^2.7.3",
+    "chart.js": "^2.9.4",
     "core-js": "^2.6.5",
     "currency-formatter": "^1.4.2",
     "firebase": "^6.6.1",