Update packages and update associated work.

[Tatsinnit]

Hiya ❤️ This PR intends to update package.json and node js modern evolution of packages and associated ways.

We should probably do a quick manual test for these changes. Any specific doc which can help for this then please do point out.

Key changes made are:

Few key things are update like vsc engine is at 1.101.0 and above rather then in old 1.31.0

1. Fixed the prepare script:

   • Before: "prepare": "node ./node_modules/vscode/bin/install && npm run compile"
   • After: "prepare": "npx @vscode/dts dev && npm run compile",
   • • @vscode/dts dev is the modern replacement for the deprecated vscode/bin/install
   • Removed the deprecated vscode/bin/install pattern

2. Updated Node.js requirements:

   • Added "node": ">=18.0.0" to engines
   • Updated @types/node from ^10.2.0 to ^20.0.0

3. Modernized dependencies:

   • TypeScript: ^3.2.2 → ^5.0.0
   • Mocha: ^4.1.0 → ^10.0.0
   • @types/mocha: ^2.2.32 → ^10.0.0
   • Removed deprecated packages (gulp, gulp-tslint, tslint)

4. Added modern linting:

   • Added ESLint with TypeScript support
   • Added lint and lint:fix scripts
   • Created .eslintrc.json configuration

5. Updated TypeScript configuration:

   • Target changed from es6 to ES2020
   • Added modern compiler options for better type safety

Replaces the old "node ./node_modules/vscode/bin/install && npm run compile" with this "prepare": "npx @vscode/dts dev && npm run compile" as the old way was giving error as its deprecated now.

❤️ How have you been @itowlson and Gentle fyi & cc: @itowlson & @squillace

Side note: Gentle fyi to @tejhan, and @bosesuneha who contributes to the extension.