MRG: replace index.md with new.md

[ctb]

Note: PR into #2184

[codecov]

Codecov Report

Merging #2809 (535d7eb) into update_doc_structure (1f44043) will not change coverage.
Report is 1 commits behind head on update_doc_structure.
The diff coverage is n/a.

@@                  Coverage Diff                  @@
##           update_doc_structure    #2809   +/-   ##
=====================================================
  Coverage                 86.26%   86.26%           
=====================================================
  Files                       130      130           
  Lines                     14742    14742           
  Branches                   2621     2621           
=====================================================
  Hits                      12717    12717           
  Misses                     1724     1724           
  Partials                    301      301           

Flag	Coverage Δ
hypothesis-py	25.82% <ø> (ø)
python	92.85% <ø> (ø)
rust	50.92% <ø> (ø)

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