using npm creates discrepancies

[Sakrecoer]

As of 71ccdcd, starting astro with the commands listed in the README.md creates a site that looks different.

Since we're now using pnpm in CI, it might be worth reflecting this in README.md.

[jaromil]

I have no idea how to use pnpm and the differences with npm. When previewing I use nvm and npm. Is this really necessary? @puria

[puria]

open to people use the tool of their choice. npm prolificates node_modules for each project. pnpm do not, mostly i use it for ecology