refactor: remove external icon libraries

package.json

@@ -26,10 +26,7 @@
     "css-vars-ponyfill": "^1.11.1",
     "current-script-polyfill": "^1.0.0",
     "element-resize-detector": "^1.2.0",
-    "flag-icon-css": "^3.2.0",
-    "font-awesome": "^4.7.0",
     "perfect-scrollbar": "^1.4.0",
-    "simple-line-icons": "^2.4.1",
     "tooltip.js": "^1.3.1",
     "vue": "^2.6.6",
     "vue-chartjs": "^3.4.0",