chore: remove unnecessary code in root's package.json

[tyankatsu0105]

• Remove description

  • I think description in root is unnecessary with Lerna
  • See: https://github.com/vuejs/vue-cli/blob/dev/package.json https://github.com/babel/babel/blob/master/package.json

• Remove main

  • It seems like unused.

[eunjae-lee]

@tyankatsu0105 would you open a pr to add yourself as a code contributor?

https://shipjs.netlify.com/guide/contributing.html#contributors-list