Fix a bug when resolving against marker traits

We don't want to resolve them and we also don't have any docs for them

Update Readme

* fixed issue with doc tests
* linked to presentation from EuroRust

define readme for `buffi` and `buffi_macro` and bump versions

also set other workspace crates to `publish = false` and fix the readme path again

fix readme link in docs

bump version

update metadata for `buffi_macro` and add categories