[Nuxt Property '$gsap' does not exist on type]

I want to usenuxt-gsap-module on my nuxt app.

I follow the docs in github : https://github.com/ivodolenc/nuxt-gsap-module

but I can't acces to this.$gsap in may pages and components, it throws an error :  Property '$gsap' does not exist on type 'XXX'

my package.json file

 

"devDependancies" : {

"nuxt-gsap-module": "1.7.1"

}

 

index.vue 

boxRotation (): void {

    const gsap = this.$gsap

    gsap.to('.box', { rotation: 27, x: 100, duration: 1 })

  }

  mounted () :void {

    this.boxRotation()

  }

 

nuxt.config.js

 

 

buildModules: [

    '@nuxt/typescript-build',

    'nuxt-gsap-module'

  ],