Switch to pnpm

[logbasem]

Switch to pnpm from npm for much faster project management functionality¹.

Checklist

If you complete all these tasks, please close the issue. :D

• Change documentation to use pnpm commands instead of npm
  • npm => pnpm
    • Most commands map directly. e.g., npm i is just pnpm i
  • npx => pnpm exec
    • This command uses the project's dependencies.
    • If you just want anything from the package registry, you can use pnpm dlx instead
      • ex: use pnpm dlx create-next-app@latest to replace npx create-next-app@latest

Footnotes

1. Recommendation from a PR review: https://github.com/Sooner-Rover-Team/RoverMap/pull/13#discussion_r2098257288 ↩