Fix response encoding detection

[elacuesta]

Fixes #64

[codecov]

Codecov Report

Merging #65 (c202855) into master (4b7134e) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #65   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          209       221   +12     
=========================================
+ Hits           209       221   +12     

Impacted Files	Coverage Δ
scrapy_playwright/handler.py	100.00% <100.00%> (ø)

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