feat: typescript support

[andrewsantarin]

This PR adds type definition modules so that React TypeScript projects using this library do not need to introduce a drop-in module augmentation of their own, such as in this example gist.

Resolves #346.

Description

• Added .d.ts modules for all .js files exported by this library.
• Added compilation script for said .d.ts modules.
• Added TypeScript component .ts(x) tests in src/components/__tests__ alongside the existing .js tests.
• Added mentions of TypeScript support, usage examples and contribution instructions in README.md.
• Added lint support for the TypeScript modules.

Demo:

Locally via yalc

1. Install yalc globally.

   npm i -g yalc

2. Prepare react-intl-tel-input for local-only publishing.

   yarn build
   yalc publish --no-scripts # skips prebuild to unblock you

3. Scaffold a React app.

   npx create-react-app react-intl-tel-input-typescript-demo --template typescript

4. Install the simulated react-intl-tel-input package.

   yalc add react-intl-tel-input

5. Use react-intl-tel-input in the React app: App.tsx

   import IntlTelInput from 'react-intl-tel-input';

6. Inspect IntlTelInput to see its TypeScript definitions.

Remotely via CodeSandbox

A live preview is available with a pre-merge variant of this library: @andrewsantarin/react-intl-tel-input.

Note: The pre-merge variant is somewhat behind in CI changes from master, but the module type definitions are still up to date.

Types of changes

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

Checklist:

• I have used ESLint & Prettier to follow the code style of this project.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.