fix(VDatePicker): events alignment on current date

[jacekkarczmarczyk]

Motivation and Context

fixes #8182

How Has This Been Tested?

unit, playground

Markup:

<template>
  <v-container>
    <v-date-picker value="2020-01" :events="['2020-11', '2020-12']" show-current="2020-11" type="month"></v-date-picker>
    <v-date-picker value="2020-11-01" :events="['2020-11-05', '2020-11-06']" show-current="2020-11-05" type="date"></v-date-picker>
  </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)