Document webpack change: Hide orphan modules in Stats

[webpack-bot]

A pull request by @ooflorent was merged and maintainers requested a documentation change.

See pull request: webpack/webpack#7812

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A module is an orphan if it is not included in any chunk. Orphans modules are now hidden by default in Stats.

What kind of change does this PR introduce?

feature

Did you add tests for your changes?

yes

Does this PR introduce a breaking change?

yes

What needs to be documented once your changes are merged?

New stats option orphanModules, defaults to false.

[jeffin143]

@montogeek , this is completed