Document webpack change: fix resource name when filename is data uri

[webpack-bot]

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

See pull request: webpack/webpack#15293

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What kind of change does this PR introduce?

fixes #13835

• infer extension from mime type
• set path like replacement to empty string

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?

for assets builded from data uri replacements:
[name], [file], [query], [fragment], [base], [path] set to empty string

[snitin315]

I will document it.