message: refactor(button): change way to get css
diff: <template>
  <component
  :is="href ? 'a' : 'button'"
  - :class="['btn', color, variant, size, isLoading ? 'isLoading' : '']"
  + :class="btnClass"
  :href="href"
  :role="href ? '' : 'button'"
  :aria-busy="isLoading"
  @@ -46,6 +46,16 @@ export default class Button extends Vue {
  @Prop({ default: 'medium' }) size!: IButton['size']
  @Prop({ default: false }) isLoading!: IButton['isLoading']
  @Prop() href!: IButton['href']
  +
  + get btnClass() {
  + return [
  + 'btn',
  + this.color,
  + this.variant,
  + this.size,
  + this.isLoading ? 'isLoading' : '',
  + ]
  + }
  }
  </script>
  