refactor: standardized files name (#1884)

style-guide: https://panjiachen.github.io/vue-element-admin-site/guide/advanced/style-guide.html#style-guide

src/views/charts/keyboard.vue

@@ -5,7 +5,7 @@
 </template>
 
 <script>
-import Chart from '@/components/Charts/keyboard'
+import Chart from '@/components/Charts/Keyboard'
 
 export default {
   name: 'KeyboardChart',

src/views/charts/line.vue

@@ -5,7 +5,7 @@
 </template>
 
 <script>
-import Chart from '@/components/Charts/lineMarker'
+import Chart from '@/components/Charts/LineMarker'
 
 export default {
   name: 'LineChart',

src/views/charts/mix-chart.vue

@@ -5,7 +5,7 @@
 </template>
 
 <script>
-import Chart from '@/components/Charts/mixChart'
+import Chart from '@/components/Charts/MixChart'
 
 export default {
   name: 'MixChart',