fix: type nuxt 2 context with @nuxt/types

[wattanx]

🔗 Linked issue

#465

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The useContext in capi.legacy is incompatible with the useContext in @nuxtjs/composition-api.
As far as the content is concerned, it looks no different from @nuxtjs/composition-api, so I extended the type in a similar way.

https://github.com/nuxt-community/composition-api/blob/main/src/runtime/composables/context.ts#L25-L31

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[danielroe]

This looks good to me, though we may well move necessary types across from @nuxt/types and remove dependency later on, to reduce dependency on Nuxt 2-specific types, given that Bridge is meant as a temporary solution whilst migrating to Nuxt 3.