Change to pnpm as the default node package manager

[aircwo]

What

Adopt pnpm as the default package manager of choice for the playbook.

Why

pnpm is a more performant, disk space efficient, secure, and feature-rich package manager than npm. It can also be used in GitHub actions to increase performance.

Benefits of pnpm

• It is faster than npm, especially for large projects.
• It is more secure than npm, because it can verify the authenticity of dependencies.
• It has a number of features that npm does not, such as the ability to install dependencies from private repositories and the ability to manage multiple versions of a dependency.
• pnpm uses hard links and symbolic links to manage dependencies, which means that it does not need to copy dependencies to the node_modules directory.

Extra info

• Official website of pnpm.
• As the playbook is already lightweight this would be a preference more than an optimisation.
• Can be installed globally through npm 😋