fix(package): update @ng-bootstrap/ng-bootstrap to version 5.1.4

Closes #87

Author: greenkeeper[bot]

demo/package.json

@@ -41,7 +41,7 @@
     "@angular/pwa": "^0.10.7",
     "@angular/router": "^7.2.10",
     "@angular/service-worker": "^7.2.10",
-    "@ng-bootstrap/ng-bootstrap": "^4.1.0",
+    "@ng-bootstrap/ng-bootstrap": "^5.1.4",
     "bootstrap": "^4.3.1",
     "core-js": "^2.6.5",
     "font-awesome": "^4.7.0",