fix(VAvatar): add style for start, end props same as VIcon

Author: SonTT19

packages/vuetify/src/components/VAvatar/VAvatar.sass

@@ -24,6 +24,12 @@
   &--rounded
     @include tools.rounded($avatar-rounded-border-radius)
 
+  &--start
+    margin-inline-end: $avatar-margin-start
+
+  &--end  
+    margin-inline-start: $avatar-margin-end
+
   .v-img
     height: 100%
     width: 100%

packages/vuetify/src/components/VAvatar/_variables.scss

@@ -14,6 +14,8 @@ $avatar-plain-opacity: .62 !default;
 $avatar-rounded-border-radius: variables.$border-radius-root !default;
 $avatar-vertical-align: middle !default;
 $avatar-width: 40px !default;
+$avatar-margin-end: map.get(variables.$grid-gutters, 'md') !default;
+$avatar-margin-start: map.get(variables.$grid-gutters, 'md') !default;
 
 $avatar-sizes: () !default;
 $avatar-sizes: functions.map-deep-merge(