Added .d.ts extension to import type

[Secreto31126]

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with npm run test and lint the project with npm run lint and npm run prettier

As recommended in #376, I tested the library with https://arethetypeswrong.github.io/, and adding the .d.ts file extensions makes the 🥴 go away, so yeah, I think this is a keeper.

[github-actions]

Visit the preview URL for this PR (updated for commit 59fc38d):

https://whatsappapijs--pr398-test-extension-k6d9ev70.web.app

_{(expires Thu, 09 Jan 2025 08:08:30 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: 80a8dc4ceea5c783aae1d47b75797ee5b6c2f4be}