Changed CSS to SASS

Facilitating work on the project with the use of css styles.
It allows you to implement functions from other packages, e.g. bootstrap.

src/main.js

@@ -2,7 +2,7 @@ import Vue from 'vue'
 import App from './App.vue'
 import router from './router'
 import 'bootstrap'
-import 'bootstrap/dist/css/bootstrap.min.css'
+import 'bootstrap/scss/bootstrap.scss'
 
 Vue.config.productionTip = false