[2.0] Major package upgrades, better TypeScript support, smaller build

[SanderMuller]

This PR modernizing the library with upgraded dependencies, enhanced TypeScript support, and improved compatibility with modern Node.js environments.

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Key Changes

1. Node.js Version Upgrade:

   • Dropped support for Node.js 10.
   • Laravel Echo now requires Node.js 20+.

2. TypeScript Enhancements:

   • Upgraded TypeScript from V4 to the latest V5.7
   • Refined type definitions for Pusher, Socket.IO, and custom broadcasters.
   • Improved IntelliSense and stricter type checking for better developer experience.
   • Requires TypeScript 5.7+.

3. Dependency Upgrades:

   • Updated several dependencies to their latest secure versions, addressing vulnerabilities in older packages such as glob.
   • Upgraded Rollup, ESLint, and related plugins for improved performance and maintainability. This includes an upgrade to the ESlint flat file config system.
   • Made sure external optional dependencies like vue, axios, jquery, and @hotwired/turbo are not bundled.

4. Modernized Build Process:

   • Optimized Rollup configuration for ES modules and CommonJS outputs.
   • Added support for dynamic imports to handle optional dependencies gracefully.

5. Developer Experience Improvements:

   • Updated ESLint configuration to use the flat config system in ESLint 9.
   • Streamlined TypeScript and build setups for faster iterations.

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Breaking Changes (Contributor only)

1. Node.js Requirement (Contributor only):

   • Minimum Node.js version: 20+.
   • Consumers using the distributed package (NPM / dist/) are unaffected.

2. TypeScript Compatibility (Contributor only):

   • TypeScript 5.7 or newer is required for compatibility with updated type definitions.
   • The compiled output remains compatible with earlier TypeScript versions.

3. ESLint Config (Contributor only):

   • Migrated to ESLint 9's flat configuration system, which may require adjustments in custom setups.

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Benefits

• Improved Type Safety: Better typings for broadcasters and optional dependencies.
• Faster Builds: Optimized Rollup configuration and dependency updates.
• Reduced Bundle Sizes: Rollup upgrade & configuration and Typescript import as type improvements result in reduced bundle size (151KB -> 140KB for the entire dist folder, 43KB -> 29KB for echo.iife.js).
• Security Improvements: Vulnerable packages like glob have been updated to secure versions as well as Eslint major upgrade.
• Future-Proofed: Compatibility with modern Node.js and TypeScript environments.

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Testing done

1. Jest still passes.
2. I have tested the above changes on a Pusher and Reverb setup locally in two big projects leveraging websockets. Both using Webpack with Laravel Mix.
3. Eslint and TypeScript have way better coverage now as well.

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[taylorotwell]

Why do these need to be renamed?

[SanderMuller]

This tells ESlint that it's an unused argument

[taylorotwell]

Thanks @SanderMuller!

[nandi95]

@SanderMuller Thanks for doing this!
Can you perhaps look at this PR see if anything is usable from it here? https://github.com/laravel/echo/pull/356/files