fix(VBtn): only show focus if activated by keyboard

[KaelWD]

Resolves #3923
Resolves #8572
Resolves #9808

Only works in browsers that support :focus-visible, webkit just shows the normal focus overlay (including on click 😠). It is possible to polyfill this but idk how that behaves with @supports

• https://www.npmjs.com/package/focus-visible
• https://www.npmjs.com/package/postcss-focus-visible

Markup:

<template>
  <v-app>
    <v-container>
      <v-btn variant="text" color="primary">Button</v-btn>
      <v-btn variant="contained-text" color="primary">Button</v-btn>
      <div class="my-5" />
      <v-btn color="primary">Button</v-btn>
    </v-container>
  </v-app>
</template>

Peek.2021-08-16.00-11.mp4

[kingyue737]

Will this fix be merged into version2 ?

[KaelWD]

No