adding the branch in asciidoc attributes to let the .adoc use that for conditions

Overall idea is to let the .adoc use conditional blocks based on the branch:

ifeval::["{docbranch}" != "master"]
TIP: this is a development release
endif::[]

It reads the branch from the file.src.origin or file.origin or default to "unknown" (which is unlikely but possible for local unmanaged sources).