docs: Add documentation for reply accepting a function as the data parameter

[p16]

Following up from this discussion #1185 I thought there was a missing bit in the doc around the fact that the reply data parameter can be a function that will have the mocked request options as input .

[codecov-commenter]

Codecov Report

Merging #1456 (4182fea) into main (324beb6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1456   +/-   ##
=======================================
  Coverage   94.42%   94.42%           
=======================================
  Files          49       49           
  Lines        4271     4271           
=======================================
  Hits         4033     4033           
  Misses        238      238           

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[p16]

The failed test

not ok 9 - test/fetch/headers.js # time=4684.681ms
  ---
  env: {}
  file: test/fetch/headers.js
  timeout: 60000
  command: C:\hostedtoolcache\windows\node\16.15.0\x64\node.exe
  args:
    - --expose-gc
    - --experimental-wasm-simd
    - test/fetch/headers.js
  stdio:
    - 0
    - pipe
    - 2
  cwd: D:\a\undici\undici
  exitCode: null
  signal: SIGTERM
  ...

is it a known "flaky" test? it seems something related to the platform more than to the test 🤔

[mcollina]

lgtm

[mcollina]

Please update the PR title an action fails.

[p16]

@mcollina @Fdawgs It seems that the build on latest windows and node 16 is failing ontest/redirect-stream.js (same test result shown in previous message). There is nothing more than what I reported above in the log of that failure. I do not have a window machine ready to test this, is there anyone else that can have a look?

[kibertoad]

Documentation deployment is failing now: https://github.com/nodejs/undici/runs/6558409571?check_suite_focus=true