feat(VWindow,VCarousel): **prev** and **next** slots

[jacekkarczmarczyk]

Description

Adds slots for prev/next arrow

Motivation and Context

fixes partially #3235

How Has This Been Tested?

playground

Markup:

<template>
  <v-container>
    <v-window
      reverse
      show-arrows
    >
      <template #prev="{ on, attrs }">
        <v-btn
          color="success"
          v-bind="attrs"
          v-on="on"
        >Prev</v-btn>
      </template>
      <template #next="{ on, attrs }">
        <v-btn
          color="info"
          v-bind="attrs"
          v-on="on"
        >Next</v-btn>
      </template>
      <v-window-item
        v-for="n in 3"
        :key="`card-${n}`"
        class="pa-12"
      >Lorem ipsum</v-window-item>
    </v-window>

    <v-carousel>
      <template #prev="{ on, attrs }">
        <v-btn
          color="success"
          v-bind="attrs"
          v-on="on"
        >Prev</v-btn>
      </template>
      <template #next="{ on, attrs }">
        <v-btn
          color="info"
          v-bind="attrs"
          v-on="on"
        >Next</v-btn>
      </template>
      <v-carousel-item
        v-for="i in 6"
        :key="i"
      >
        <div class="black--text">
          Slide {{ i + 1 }}
        </div>
      </v-carousel-item>
    </v-carousel>
  </v-container>
</template>

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any features but makes things better)

Checklist:

• The PR title is no longer than 64 characters.
• The PR is submitted to the correct branch (master for bug fixes and documentation updates, dev for new features and backwards compatible changes and next for non-backwards compatible changes).
• My code follows the code style of this project.
• I've added relevant changes to the documentation (applies to new features and breaking changes in core library)

[nekosaur]

There's no need to repeat the slot definition or translation. Add source: 'v-window' to the definition in maps/v-window.js and then re-use them in maps/v-carousel.js (same way as v-data-table map re-uses v-data-iterator slots). Then translation is only necessary for v-window.json

updated

[KaelWD]

This doesn't entirely resolve #3235 though, you still can't modify the delimiters.

delimiter slot on the way

[jacekkarczmarczyk]

Adding delimiter slots needs some more decisions and would be done in a separate PR, i've updated description

fixes partially #3235