External links from markdown files not parsed correctly

[derhansen]

At least some external links generated from markdown files are not working as expected.

Example: https://api.typo3.org/master/md__mnt_doxygen__s_e_c_u_r_i_t_y.html

Links to our security advisories or to our PGP Public Keys result in a 404 error, since links are prepended with a ‪