Yarn update should use install instead of upgrade

[Upgrade](https://yarnpkg.com/en/docs/cli/upgrade) will update all packages to lastest version.

[Install](https://yarnpkg.com/en/docs/cli/install) not.

If I create a project, then I need add a package after few days. `upgrade` will update all packages, `install` will only install that package I need. I think `install` is correct.