Add installation size metrics to benchmarks

[lukewhitehouse]

The benchmarks on the pnpm website are a great starting point for anyone like me who's been conducting an investigation into a dependency management strategy for my company. However, I've noticed that the benchmarks don't include installation size (in terms of the package manager's store/cache, and the node_modules folder if relevant), and I was wondering if thats something that could be considered going forward?

[zkochan]

Here's an article about disk space usage of pnpm compared to npm/yarn: https://www.voitanos.io/blog/npm-yarn-pnpm-which-package-manager-should-you-use-for-sharepoint-framework-projects/

The difference on a single project (like on the benchmark project) doesn't showcase the benefit of pnpm's global store as the disk space savings come when you run install on several projects on your computer.