Add special non-word UTF8 characters to allowed symbols

As seen in https://gitlab.archlinux.org/klausenbusk/management-repo/-/jobs/87537 certain non-word UTF8 characters such as the ™ symbol are not covered in the RELATIVE_PATH regular expression and need to be added. See e.g. https://stackoverflow.com/questions/15125465/python-regex-and-the-copyright-symbol for a solution to the problem.