pnpm cache could prune store before caching #1428

Description:

To avoid the pnpm store growing with each update of packages, the action could guarantee that the cached store is as narrow as possible by running pnpm store prune before storing the cache.

This should result in cache not ballooning over time, and avoiding caching unused packages.

Justification:

Could result in quicker cache save/restore for long running workflows using cache: 'pnpm'

Are you willing to submit a PR?

Yeah I could look at it, if it's something people agree would be useful