Document webpack change: add some types

[webpack-bot]

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

See pull request: webpack/webpack#7786

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What kind of change does this PR introduce?
types

Did you add tests for your changes?
N/A

Does this PR introduce a breaking change?
yes

What needs to be documented once your changes are merged?
Migration guide:
Module.nameForCondition Module.updateCacheModule and Module.chunkCondition are no longer optional. Module should extend Module and this is no problem.