patch 9.1.0897: filetype: pyrex files are not detected

patch 9.1.0897: filetype: pyrex files are not detected

Problem:  filetype: pyrex files are not detected
Solution: detect '*.pxi' and '*.pyx+' as pyrex filetype
          (user202729)

References:
https://cython.readthedocs.io/en/latest/src/userguide/language_basics.html#cython-file-types
https://www.csse.canterbury.ac.nz/greg.ewing/python/Pyrex/version/Doc/Manual/using_with_c++.html

closes: #16136

Signed-off-by: user202729 <25191436+user202729@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>