ci: Add bender-up-to-date action

Created by: niwis

To check if Bender.yml is up-to-date.

As expected, the workflow fails due to

bender-up-to-date: /home/runner/work/cva6/cva6/core/include/ariane_rvfi_pkg.sv not found.
bender-up-to-date: /home/runner/work/cva6/cva6/core/ariane.sv not found.

This will be resolved in #1189 and #1190, after which I will rebase and this job should pass.