Fix Nuxt Composition

[Maronato]

Description

Currently it is not possible to use the built-in composition library with nuxt because the provide scope is not shared by nuxt's instance.
This PR creates a new export useToast from "vue-toastification/composition/nuxt":

// MyComponent.vue
// Import from vue-toastification/composition/nuxt, not vue-toastification/composition
import { useToast } from "vue-toastification/composition/nuxt";
// Then, in the setup method
  setup() {
    const toast = useToast()
    // Use it like you would use this.$toast
  }

It also fixes typing issues mentioned in #180

Related Issue

closes #180

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• [ x New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #287 (dda988c) into main (1ad2724) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main      #287   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           14        14           
  Lines          436       436           
  Branches        89        89           
=========================================
  Hits           436       436           

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