Deprecated npm package should be marked deprecated on npm

[mikemaccana]

Speaking to Metaplex, this package is deprecated, but not marked as deprecated as npm.

See https://docs.npmjs.com/deprecating-and-undeprecating-packages-or-package-versions

Run the command:

npm deprecate @metaplex-foundation/js "This package is now deprecated, see https://developers.metaplex.com/token-metadata/getting-started/js for up to date docs on creating NFTs using Metaplex Token Metadata."

This will point users of the old npm package to the Umi docs.