feat: Support any content type ending in +json [#706].

[dbanty]

Thanks @XioNoX and @mtovt!

[codecov]

Codecov Report

Merging #709 (8aaecf1) into main (e7a4e71) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #709   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           49        49           
  Lines         1954      1962    +8     
=========================================
+ Hits          1954      1962    +8     

Impacted Files	Coverage Δ
openapi_python_client/parser/openapi.py	100.00% <100.00%> (ø)
openapi_python_client/parser/responses.py	100.00% <100.00%> (ø)

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