pubspec.yaml on all packages to include homepage link

[slightfoot]

homepage link to main repo homepage.
repo link to packages// page.

[miquelbeltran]

Template:

homepage: https://plus.fluttercommunity.dev/
repository: https://github.com/fluttercommunity/plus_plugins/tree/main/packages/

[miquelbeltran]

Fixed in #29