[Feature] pnpm/corepack support

Feature Request

From https://github.com/microsoft/Oryx/issues/1150#issuecomment-1886067023

We're not currently looking to support pnpm. Closing this issue for now, please create a new issue and link to this one if you feel strongly.

I feel strongly about this and decided to open a new issue.

My suggestions is at follows:

• Detect presence of packageManager key in package.json.
• If found,
  • Run corepack enable
  • Run npm install / yarn install / pnpm install depending on the package manager name
• If not found,
  • Just run npm install as before

How this will improve things:

• Azure Static Site and Azure Web Service users can build their app without having to set up PRE_BUILD_COMMAND and CUSTOM_BUILD_COMMAND. I use Netlify and Vercel, and they are supported out-of-the-box, so I expect the same in other hosting services. Azure services not recognizing pnpm in my project is a turn off for me.

• GitHub Codespaces currently run npm install even in pnpm projects. This means not only it takes a longer time for Codespace to initialize pnpm projects (due to waiting for npm install), afterwards I have to go ahead and rm -rf node_modules package-lock.json and run pnpm install again.

In short, supporting pnpm via corepack will improve both developer experience in Codespaces and deployment experiences in Azure services.