docs(MdFile): add missing required v-model

docs/app/pages/Components/File/examples/FileField.vue

@@ -2,43 +2,45 @@
   <div>
     <md-field>
       <label>Single</label>
-      <md-file/>
+      <md-file v-model="single" />
     </md-field>
 
     <md-field>
       <label>Upload files</label>
-      <md-file placeholder="A nice input placeholder"/>
+      <md-file v-model="placeholder" placeholder="A nice input placeholder" />
     </md-field>
 
     <md-field>
       <label>Disabled</label>
-      <md-file disabled/>
+      <md-file v-model="disabled" disabled/>
     </md-field>
 
     <md-field>
       <label>Initial value</label>
-      <md-file v-model="initial"/>
+      <md-file v-model="initial" />
     </md-field>
 
     <md-field>
       <label>Multiple</label>
-      <md-file multiple v-model="multiple"/>
+      <md-file v-model="multiple" multiple />
     </md-field>
 
     <md-field>
       <label>Only images</label>
-      <md-file accept="image/*" v-model="single"/>
+      <md-file v-model="single" accept="image/*" />
     </md-field>
   </div>
 </template>
 
 <script>
-export default {
-  name: 'FileField',
-  data: () => ({
-    initial: 'vue-material-is-awesome.jpg',
-    single: null,
-    multiple: null
-  })
-}
+  export default {
+    name: 'FileField',
+    data: () => ({
+      initial: 'vue-material-is-awesome.jpg',
+      single: null,
+      placeholder: null,
+      disabled: null,
+      multiple: null
+    })
+  }
 </script>