refactor(avatar): icon input manner

demo/demo.vue

@@ -95,7 +95,7 @@ export default {
           name: 'Common Components',
           childItems: [
             {
-              name: 'Avatar (in progress)',
+              name: 'Avatar',
               path: `/${this.lang}/${this.theme}` + '/n-avatar'
             },
             {

demo/documentation/components/avatar/enUS/icon.md

@@ -1,11 +1,9 @@
 # Icon
 ```html
 <n-avatar>
-  <template v-slot:icon>
-    <n-icon>
-      <md-cash />
-    </n-icon>
-  </template>
+  <n-icon>
+    <md-cash />
+  </n-icon>
 </n-avatar>
 ```
 ```js

styles/Avatar.scss

@@ -12,9 +12,7 @@
       line-height: 1.25;
     }
     @include b(icon) {
-      position: relative;
-      top: 4px;
-      font-size: $width - 8px;
+      font-size: $width;
     }
   }
 }
@@ -27,6 +25,7 @@
     @include b(icon) {
       transition: fill .3s $default-cubic-bezier;
       fill: white;
+      vertical-align: bottom;
     }
     color: white;
     transition: background-color .3s $default-cubic-bezier, color .3s $default-cubic-bezier;