Add read permission for npm cache

[pomdtr]

Some npm modules relies on static assets distributed on npm.

You can find it using deno info:

{
  "denoDir": "/Users/pomdtr/Library/Caches/deno",
  "modulesCache": "/Users/pomdtr/Library/Caches/deno/deps",
  "npmCache": "/Users/pomdtr/Library/Caches/deno/npm", // <- this should be whitelisted
  "typescriptCache": "/Users/pomdtr/Library/Caches/deno/gen",
  "registryCache": "/Users/pomdtr/Library/Caches/deno/registries",
  "originStorage": "/Users/pomdtr/Library/Caches/deno/location_data"
}