doc: document Brotli/iter dictionary option

[islandryu]

Ref: #64598

Document the missing dictionary option on BrotliOptions.
Note ArrayBuffer support for the node:zlib/iter dictionary option.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.13%. Comparing base (4f844f4) to head (a0d82d7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64602      +/-   ##
==========================================
- Coverage   90.13%   90.13%   -0.01%     
==========================================
  Files         741      741              
  Lines      241976   241973       -3     
  Branches    45543    45535       -8     
==========================================
- Hits       218116   218101      -15     
- Misses      15379    15382       +3     
- Partials     8481     8490       +9     

see 35 files with indirect coverage changes

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