Yarn 2 PNP fix - plugin is using loader-utils package without explicitly listing it as dependency

[Liwoj]

Yarn V2 in PNP mode refuses access to packages which are not listed as a dependency.

Details: https://yarnpkg.com/advanced/rulebook#packages-should-only-ever-require-what-they-formally-list-in-their-dependencies

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch and not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested with all Quasar themes
• Any necessary documentation has been added or updated in the docs (for faster update click on "Suggest an edit on GitHub" at bottom of page) or explained in the PR's description.

[rstoenescu]

Thanks for contributing!
This will go into vue-cli-plugin-quasar 5.0.2