chore: update curl.haxx.se URLs to curl.se and use all encodings

[puzza007]

• Update all documentation URLs from curl.haxx.se to curl.se
• Change CURLOPT_ACCEPT_ENCODING from "gzip,deflate" to "" to accept all built-in encodings (includes zstd, brotli when available)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.77%. Comparing base (83ac708) to head (5bfb634).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #166   +/-   ##
=======================================
  Coverage   72.77%   72.77%           
=======================================
  Files           6        6           
  Lines        1058     1058           
=======================================
  Hits          770      770           
  Misses        288      288           

Flag	Coverage Δ
c	72.77% <100.00%> (ø)
erlang	72.77% <100.00%> (ø)

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