Document webpack change: enforce doesn't affect minSize for maxSize

[webpack-bot]

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

See pull request: webpack/webpack#8451

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enforce now works as documented
emit warning for minSize > maxSize configuration
performance improvements
bugfix when multiple cacheGroups have the same name

fixes #8407

What kind of change does this PR introduce?
bugfix

Did you add tests for your changes?
yes

Does this PR introduce a breaking change?
yes, but a bugfix

What needs to be documented once your changes are merged?
enforce now works as documented.

Tells webpack to ignore splitChunks.minSize, splitChunks.maxSize, splitChunks.minChunks, splitChunks.maxAsyncRequests and splitChunks.maxInitialRequests options and always create chunks for this cache group.

But there is a little error in the documentation as splitChunks.maxSize is not ignored.

Tells webpack to ignore splitChunks.minSize, splitChunks.minChunks, splitChunks.maxAsyncRequests and splitChunks.maxInitialRequests options and always create chunks for this cache group.