docs(install): correct npm source, document peer deps, fix tailwind path

[maherelgamil]

Summary

• Fix description of monorail:install — says it installs from "GitHub Packages", but monorailphp is published to the npm registry.
• Document peer dependencies introduced in v0.2.0. npm 7+ auto-installs them; pnpm / yarn with strict peer resolution need an explicit install command (listed in the docs).
• Unify Tailwind @source path with the Vite input + config('monorail.assets.js_entry') — all three now point at node_modules/monorailphp/.... Previously the manual-install snippet pointed at vendor/monorail/monorail/..., which didn't match the other paths and used the old composer name.

Test plan

• Fresh Laravel + Inertia app: `composer require monorailphp/monorail` then `php artisan monorail:install` — verify the description matches what actually happens.
• pnpm consumer follows the new "Peer dependencies" block — `npm run dev` succeeds without ERESOLVE.
• Manual-install path renders an admin page using the `node_modules` source.