Update dependency html-webpack-plugin to v4.0.0-beta.8

[renovate-bot]

This PR contains the following updates:

Package	Type	Update	Change
html-webpack-plugin	devDependencies	patch	4.0.0-beta.5 -> 4.0.0-beta.8

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Release Notes

jantimon/html-webpack-plugin

### [`v4.0.0-beta.8`](https://togithub.com/jantimon/html-webpack-plugin/compare/5acac51da302451cca5b33f305d8d26c7cc2b87f...91a028f3882cfbcaca167e0826bf8e2db674caf2) [Compare Source](https://togithub.com/jantimon/html-webpack-plugin/compare/5acac51da302451cca5b33f305d8d26c7cc2b87f...91a028f3882cfbcaca167e0826bf8e2db674caf2) ### [`v4.0.0-beta.7`](https://togithub.com/jantimon/html-webpack-plugin/compare/298635f4b3fb19fe920b1e0b982b61af0f31239d...5acac51da302451cca5b33f305d8d26c7cc2b87f) [Compare Source](https://togithub.com/jantimon/html-webpack-plugin/compare/298635f4b3fb19fe920b1e0b982b61af0f31239d...5acac51da302451cca5b33f305d8d26c7cc2b87f)

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