Restrict css-minimizer-webpack-plugin version in the generator unless using Node v18+

[ahangarha]

Summary

Recently css-minimizer-webpack-plugin released v6.0.0 in which the minimum required Node version is 18.

We install this package in our generator, and we need this PR to ensure our generator doesn't break in an environment with an older Node.

~⚠️ We may need to make a release after this merge.~

~Alternatively, we can bump our Nodejs support to v18 (the current LTS)~

I have change the generator so that it limits the version of this package unless we use Node v18+.

Pull Request checklist

• [x] ~Add/update test to cover these changes~
• [x] ~Update documentation~
• [x] ~Update CHANGELOG file~

Other Information

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This change is 

[ahangarha]

I close this PR regarding this comment. The required change is applied in #1592