Update .gitattibutes file

[yunchu]

To exclude 'tab-in-indent' error from whitespace checking on Makefile

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (sphinx-docs-rework@8c5b1b0). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@                  Coverage Diff                  @@
##             sphinx-docs-rework     #893   +/-   ##
=====================================================
  Coverage                      ?   78.61%           
=====================================================
  Files                         ?      205           
  Lines                         ?    25067           
  Branches                      ?     5029           
=====================================================
  Hits                          ?    19706           
  Misses                        ?     4229           
  Partials                      ?     1132           

Flag	Coverage Δ
macos-11_Python-3.8	77.60% <0.00%> (?)
ubuntu-20.04_Python-3.8	78.60% <0.00%> (?)
windows-2019_Python-3.8	78.54% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.