Support special characters

[kjetilbk]

• Characters like Æ, Ø and Å were interpreted as ? without explicitly passing the content type to the encoder for circe, and adding charset to the json content type.

[codecov]

Codecov Report

Merging #94 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #94   +/-   ##
=======================================
  Coverage   65.11%   65.11%           
=======================================
  Files          22       22           
  Lines         579      579           
  Branches       10       10           
=======================================
  Hits          377      377           
  Misses        202      202

Impacted Files	Coverage Δ
...irce/src/main/scala/hammock/circe/CirceCodec.scala	80% <100%> (ø)	⬆️
...re/shared/src/main/scala/hammock/ContentType.scala	85.71% <100%> (ø)	⬆️

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[drskur]

I use Korean, and I got the same pain.

[pepegar]

Looks good to me. Thank you very much @kjetilbk !