Use pkgs/ instead of packages/ to align with other org mono repos

[parlough]

Moves the packages/ directory to pkgs/ to be consistent with other mono repos in the dart-lang organization. This helps me with muscle memory :)

[devoncarew]

👍 , +1 to conventions

I also like having a table of packages in the main repo readme. That may not be as important for this repo - it doesn't look like anything from here is published?

[parlough]

Thanks for taking a look!

I also like having a table of packages in the main repo readme. That may not be as important for this repo - it doesn't look like anything from here is published?

I'm planning to write a new README soon, so I'll explore that at the same time. And yeah nothing is published for now, but that might change in the future.