[Javascript] Revamp doc

[Frzk]

I was trying to fix #2615 and realized the Node.js documentation is a bit messy:

• We have a section dedicated to Node.js with a sub-section dedicated to AngularJS. On the other hand, we have bits of documentation related to Next.js or Vite in the Introduction sub-section.
• We also have a section dedicated to MeteorJS, as well as entries related to MeteorJS in the Node.js section.
• We have instructions about starting a Node.js app in both Introduction and Getting Started sub-sections.
• We have doc about Yarn 2 and 3 (but nothing about Yarn 4).
• We have no doc about pnpm.
• We have no doc about Node.js versions availability.
• ...
• There are also unresolved issues:
  • Doc buildpack nodejs yarn #2615
  • Monorepo with yarn workspaces #2507

Consequently, I'd like to suggest a new Node.js documentation structure:

---

Overview (page) -- Goal of this page is that someone can check whether Scalingo will fit or not, depending on their needs.

Some introduction blah blah

1. Runtimes
   1. Available Versions
   2. Supported Frameworks
   3. Supported Package Managers

Getting Started (page) -- Let's dive into the technical guides here.

1. Detection
2. Specifying Node.js Version
3. Choosing a Package Manager
   1. Working with npm
   2. Working with pnpm
   3. Working with Yarn
4. Configuring your Node.js App
   1. Building your Node.js App
   2. Running your Node.js App
   3. Best Practices

Troubleshooting (page) -- Don't know yet what exactly to put in there, but it might be useful.

Frameworks (section) -- A page dedicated to a few well-known frameworks: Vite, Next.js, Express.js, Meteor,...

• Meteor (page)
• Vite (page)
• Next.js (page)
• ...

---

WDYT?