Document webpack change: feat: allow initial chunks be anywhere

[webpack-bot]

A pull request by @alexander-akait was merged and maintainers requested a documentation change.

See pull request: webpack/webpack#18982

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What kind of change does this PR introduce?

feature - now link can be any place

ref: webpack/webpack#17611
ref: webpack/webpack#14893

/cc @hardfist @fi3ework @ahabhgk

Did you add tests for your changes?

Existing

Does this PR introduce a breaking change?

Yes

What needs to be documented once your changes are merged?

Yes:

• output.cssHeadDataCompression was removed