chg: ci: Check that generated changelog entry doesn't break docs build
Since changelog entries are now generated from MR title&description, they aren't sanity checked during a regular docs build. If these contain special sequences that will be interpreted by sphinx, it might result in breakage that would have to be amended manually.
Add a CI check to test a doc build with changelog after the MR is merged to ensure that the docs can be built when generating changelog from pristine git contents.
Related #4847
Edited by Petr Špaček