doc: declare Requirements & Compatibility

[tangcent]

close #993

[codecov-commenter]

Codecov Report

Merging #994 (48667f7) into master (5df49ca) will not change coverage.
The diff coverage is n/a.

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@@             Coverage Diff             @@
##              master      #994   +/-   ##
===========================================
  Coverage     59.759%   59.759%           
+ Complexity      2321      2320    -1     
===========================================
  Files            260       260           
  Lines          12296     12296           
  Branches        3053      3053           
===========================================
  Hits            7348      7348           
  Misses          3298      3298           
  Partials        1650      1650           

Flag	Coverage Δ
unittests	59.759% <ø> (ø)

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