artifact exclude rules may exclude vendor files from deploy

[jonnsn]

file config/artifact.excludes contains the path "pub/media".
This will exclude every path where this pattern is contained.
E.g. the amasty module "product-attachment" contains this path
vendor/amasty/product-attachment/pub/media/amasty/...
which will be excluded too.
Solution is to use a leading slash, which is no absolute path but relative to the sync root folder.
The other paths are imo not critic.

[jonnsn]

sorry, I am not experienced with github PR.