docs: Fix repos and homepages on pubspecs

[luanpotter]

Description

As pointed out to me by boraizzet, if you go to our pub page, this link is broken:

Because it assumes the code is in the root of the repo (https://github.com/luanpotter/audioplayers/blob/master/example/lib/main.dart). That is controlled by the repository entry on pubpsec, which we don't even have -- so i falls back to homepage.

So this PR fixes a few issues with our pubspec setup regarding the repo:

• fixes the old repo url to the new bluefire one
• add both homepage and repository as they are different things
• homepage still points to the root of the repo for the nice readme -- for now
• repository points to the actually repository folder inside the blob/master

This is in line with how other mono-repos do it, for example firebase_core

Note that each package has a symlink for the readme so that should work fine.

I believe this fixes all the problems, but please lmk if it makes sense.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs:, chore: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation and added dartdoc comments with ///, where necessary.
• I have updated/added relevant examples in example.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

[Gustl22]

I also noticed in the README that the build status and the badge resource still points to your repository. Maybe we could include this into this PR.

[luanpotter]

@Gustl22 good catch, updated