Provide yarn alternative in missing dependency error

[rchl]

Since yarn is popuplar in nuxt ecosystem, It would probably make sense to also mention command for yarn for installing depedency.

https://github.com/nuxt/friendly-errors-webpack-plugin/blob/6052e5a3e0f1e5e2f937205c5de8d01a0506e101/src/formatters/moduleNotFound.js#L23-L26

[rchl]

Although this warning is rarely accurate as it mentions just files that don't exist as packages. :)