Content decoding relies on charset

[mirwan]

UTF-8 decoding fails when non UTF-8 content is returned (ex: French and Portuguese of https://www.addic7ed.com/serie/Evil/4/4/How_to_Build_a_Coffin)

With this PR, content is decoded if a charset is present (English and Portuguese in the example) or directly returned if no t (French in the example)

[romanvm]

Also please update your PR with the recent master to fix the linter check errors.

[romanvm]

Thanks