Docs: Mention fnm support to resolve pnpm version in contribution guide

[larsrickert]

Update our contribution guide to mention fnm feature to resolve pnpm version so there is no need to manage/install it manually:

1. Run corepack enable once
2. Add eval "$(fnm env --use-on-cd --version-file-strategy=recursive --corepack-enabled --resolve-engines)" to your ~/.zshrc file

[larsrickert]

Hmm this only works when manually executing fnm use and is not automatically performed when opening a terminal...not sure if this is a good recommendation then

[JoCa96]

@larsrickert It needs to configured in your .zshrc / .bash_profile :

# fnm
export PATH="/Users/carlej/Library/Application Support/fnm:$PATH"
eval "$(fnm env --use-on-cd --corepack-enabled --resolve-engines)"

[larsrickert]

@larsrickert It needs to configured in your .zshrc / .bash_profile :

It works now! I needed for first one corepack enable once.