fix: Ensure Reactivity for 'to' Attribute in useLink Composable

[rbgmulmb]

Description

This PR addresses the following issue:
If a component is initialized without the toattribute, adding the attribute later does not involve the client-side router anymore. Clicking on such a component causes the entire application to reload. This issue is caused by the navigate and route properties returned by the useLink composable not being reactive. This PR adds reactivity to these properties.

Additionally, this PR includes unit tests for the useLink composable to ensure its functionality and correctness.

Markup:

In the current version, clicking on the 'Not Working' card causes the entire application to reload.
In the fixed version, it utilizes the client-side router.

<template>
  <v-app>
    <v-container>
      <v-card
        :to="workingTo"
        color="blue"
        height="100"
        width="200"
      >Working</v-card>
      <v-card
        :to="notWorkingTo"
        color="pink"
        height="100"
        width="200"
      >Not Working</v-card>
    </v-container>
  </v-app>
</template>

<script setup>
  import { ref } from 'vue'

  const workingTo = ref({ name: 'page1' })
  const notWorkingTo = ref(null)

  setTimeout(() => {
    notWorkingTo.value = { name: 'page1' }
  }, 1000)
</script>