Filter out invalid bins when loading package manifest

[charlespierce]

Info

• Reported in Discord: https://discord.com/channels/413753499835301908/413753499835301917/845139760993402891
• If a package has an invalid name in the bin hash in package.json, both npm and Yarn handle it by skipping over that entry, but Volta tries to create shims and then fails with an error.
• We should match the behavior of the package managers and skip over invalid entries (ones that contain path separators).

Changes

• Updated the logic for parsing the bin hash to exclude any names that contain path separators (/ and \).

Tested

• Installed the example from Discord (@ethersphere/swarm-cli) and confirmed that it failed before the change and succeeded afterwards.
  • Note: npm version 6 and lower appear to do some normalization of the package.json during a global install, so I was only able to reproduce the failure using npm 7.