chore(readme): fix invalid links

[paulocuambe]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Some of the links on README are incorrect.
This PR fixes the links in the core team section concerning bug reports, code, documentation, tests.
The links I fixed were pointing to github.com/Atinux/Nuxt/{something}, this change points them to github.com/nuxt/nuxt.js/{something}.

NOTE: I noticed while creating this PR that there is a note to not modify the section. If this PR is violating something you can close it.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[Atinux]

Thank you!

[paulocuambe]

First of many I hope🎉.