Package check should check URLs

[mcm1957]

Package check should check that the following urls at io-package.json refer to the correct location:

common.readme
common.exticon

Especially when changing master / main those urls are often missed to be updated.

[Apollon77]

How to determine "correct" location? Just "no error when getting them"?

[mcm1957]

I would not check if the files are getable. This could be a problem with early PRs.

The format of the files is ruther fixed. So the repoowner and the reponame could be checked. And the head bfracnh is also clearly defined.README.md must be at root of repo so the url is clearly defined by owner, adaptername and README.md. (And this leads to the question why we put the info into io-package.json at all...)

The same is valid for exticon except the filename. Here one could check if the file exists,

Typical errors are wrong owner and even more wrong head baranch (master -> main)