Document webpack change: allow to move modules to parent chunks

[webpack-bot]

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

See pull request: webpack/webpack#11529

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What kind of change does this PR introduce?
bugfix

Did you add tests for your changes?
yes

Does this PR introduce a breaking change?
no

What needs to be documented once your changes are merged?
splitChunks.cacheGroups.*.name can be used to move modules into a chunk that is a parent of the source chunk. Examples: name: "runtime" to move modules into the runtime chunk, name: "entry-name" to move modules into the entry chunk. On demand named chunks can also be used, but one have to be careful that the selected modules are only used below this chunk.

[rahul3v]

I believe it's name: "entry-name" to move modules into the entry-name chunk, right! , like inside entry-name.js file,

This is my first time and i believe I can document this one