docs(compression): deprecate ContentEncoding, add CAFxX recipe

[fredbi]

Mark negotiate.ContentEncoding deprecated — the runtime does not ship compression. Add a runnable example under
docs/examples/middleware/compression/ showing composition with github.com/CAFxX/httpcompression at the http.Handler level. The example lives in its own go module (registered in go.work) so CAFxX is not pulled into the root go.mod.

• closes middleware: misleading function ContentEncoding does not implement any compression #440

Change type

Please select: 🆕 New feature or enhancement|🔧 Bug fix'|📃 Documentation update

Short description

Fixes

Full description

Checklist

• I have signed all my commits with my name and email (see DCO. This does not require a PGP-signed commit
• I have rebased and squashed my work, so only one commit remains
• I have added tests to cover my changes.
• I have properly enriched go doc comments in code.
• I have properly documented any breaking change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.04%. Comparing base (5a88ba4) to head (dfd88b2).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #447   +/-   ##
=======================================
  Coverage   85.04%   85.04%           
=======================================
  Files          60       60           
  Lines        3978     3978           
=======================================
  Hits         3383     3383           
  Misses        451      451           
  Partials      144      144           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.