Add more common MS Office file extensions to exclude for documents

[mikkeschiren]

MS Office Word template file has dotx file ending, I think it could be a good idea to exclude it.

[codecov]

Codecov Report

Merging #6074 (523521d) into master (4abc54f) will increase coverage by 0.06%.
The diff coverage is n/a.

❗ Current head 523521d differs from pull request most recent head da6e75d. Consider uploading reports for the commit da6e75d to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6074      +/-   ##
==========================================
+ Coverage   88.88%   88.95%   +0.06%     
==========================================
  Files         163      163              
  Lines       11571    11571              
  Branches     1876     1876              
==========================================
+ Hits        10285    10293       +8     
+ Misses        975      969       -6     
+ Partials      311      309       -2     

Files	Coverage Δ
scrapy/linkextractors/__init__.py	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

[wRAR]

Thanks!