feat: make build-info browser compatible

[lukasholzer]

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Summary

Fixes https://github.com/netlify/pillar-workflow/issues/1011

Optimisations on the WebFS where not done (to reduce http calls)
I will do this in a follow up PR as this is already a huger PR size.

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[github-actions]

This pull request adds or modifies JavaScript (.js, .cjs, .mjs) files.
Consider converting them to TypeScript.

[danez]

Looks really good.

[danez]

Just noting that path is easy to polyfill in the browser, so we do not necessarily need to add it to the FileSystem here, but I'm also not against doing that.

[lukasholzer]

But then you would need webpack ;) and I've built an implementation for it (added good tests as well)