fix(VIcon): fixes accessibility issue

[tmasrat]

Description

If an icon is clickable, keyboard navigation to the icon should be allowed. If onClick is defined, I am setting the tabindex to 0
resolves vuetifyjs#18482

Markup:

<template>
  <v-app>
    <v-container>
      <v-select
          clearable
          label="Select"
          :items="['California', 'Colorado', 'Florida', 'Georgia', 'Texas', 'Wyoming']"
      ></v-select>
    </v-container>
  </v-app>
</template>