add python2/pip2 install documents

[nautaa]

What problem were solved in this pull request?

Issue Number: close #xxx

Problem:

What is changed and how it works?

Other information

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.21%. Comparing base (a67affd) to head (02c3afd).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #570   +/-   ##
=======================================
  Coverage   55.20%   55.21%           
=======================================
  Files         178      178           
  Lines       10338    10338           
=======================================
+ Hits         5707     5708    +1     
+ Misses       4631     4630    -1     

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