supabase functions serve and private packages

[elyobo]

Is your feature request related to a problem? Please describe.

Support for .npmrc authentication for private packages was added in supabase/edge-runtime#427 but in order for private packages to work a .npmrc needs to be placed in the directory for each and every function.

Describe the solution you'd like

For local development, it would be great to respect the general .npmrc rules (find the cloest up the directory structure).
For deployment to production, a .npmrc in supabase/functions that's used for all would probably make sense (and this would fit with the suggestion above).

Describe alternatives you've considered

Adding .npmrc to the .gitignore and copying them to each directory as required is viable, but the requirement should be spelled out in docs I guess (although I don't know where I would have expected to find them).

Additional context
N/A