Include npmPackage in all our plugins

[kanej]

Installing a viem project, deleting viem, and trying to connect to a network doesn’t properly detect the installation issue — it fails with a more generic “module not found” error.

We are missing npmPackage from all of our plugins’ index.ts files. This should allow for a more specific error based on expected dependencies not being installed.

Feedback from Pato on the Hardhat Alpha.