docs(vue): update markdown format for vue files.

core/src/components/action-sheet/readme.md

@@ -192,7 +192,7 @@ export default class ActionSheetExample extends Component<Props, State> {
 
 ### Vue
 
-```vue
+```html
 <template>
   <IonVuePage :title="'Action Sheet'">
     <ion-button @click="presentActionSheet">Show Action Sheet</ion-button>

core/src/components/action-sheet/usage/vue.md

@@ -1,4 +1,4 @@
-```vue
+```html
 <template>
   <IonVuePage :title="'Action Sheet'">
     <ion-button @click="presentActionSheet">Show Action Sheet</ion-button>

core/src/components/alert/readme.md

@@ -803,7 +803,7 @@ export default class AlertExample extends Component<Props, State> {
 
 ### Vue
 
-```vue
+```html
 <template>
   <IonVuePage :title="'Alert'">
     <ion-button @click="presentAlert">Show Alert</ion-button>

core/src/components/alert/usage/vue.md

@@ -1,4 +1,4 @@
-```vue
+```html
 <template>
   <IonVuePage :title="'Alert'">
     <ion-button @click="presentAlert">Show Alert</ion-button>

core/src/components/loading/readme.md

@@ -144,7 +144,7 @@ export class LoadingExample extends Component<Props, State> {
 
 ### Vue
 
-```vue
+```html
 <template>
   <IonVuePage :title="'Loading'">
     <ion-button @click="presentLoading">Show Loading</ion-button>

core/src/components/loading/usage/vue.md

@@ -1,4 +1,4 @@
-```vue
+```html
 <template>
   <IonVuePage :title="'Loading'">
     <ion-button @click="presentLoading">Show Loading</ion-button>

core/src/components/modal/readme.md

@@ -180,7 +180,7 @@ export class ModalExample extends Component<Props, State> {
 
 ### Vue
 
-```vue
+```html
 <template>
   <div>
     <ion-header>
@@ -209,7 +209,7 @@ export default {
 </script>
 ```
 
-```vue
+```html
 <template>
   <ion-page class="ion-page" main>
     <ion-content class="ion-content" padding>

core/src/components/modal/usage/vue.md

@@ -1,4 +1,4 @@
-```vue
+```html
 <template>
   <div>
     <ion-header>
@@ -27,7 +27,7 @@ export default {
 </script>
 ```
 
-```vue
+```html
 <template>
   <ion-page class="ion-page" main>
     <ion-content class="ion-content" padding>