Document webpack change: refactor chunk id plugins

[webpack-bot]

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

See pull request: webpack/webpack#7995

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• fixed sorting of assets in stats
• NamedChunkIdsPlugin can now generate ids from requests
• fixed a bug with 0 and compareSelect

What kind of change does this PR introduce?
refactoring

Did you add tests for your changes?
existing test

Does this PR introduce a breaking change?
yes, some plugin names changed

What needs to be documented once your changes are merged?

• webpack.NamedChunksPlugin -> webpack.ids.NamedChunkIdsPlugin
• webpack.optimize.OccurrenceChunkOrderPlugin -> webpack.ids.OccurrenceChunkIdsPlugin
• Compilation.hooks.optimizeChunkOrder removed
• Compilation.hooks.chunkIds added

[Lalitha-Iyer]

Do we need to document this change
webpack.NamedChunksPlugin -> webpack.ids.NamedChunkIdsPlugin
Looks like in v5 we recommend using optimization.chunkIds: 'named' instead of NamedChunksPlugin