Upgrade css-loader to 2.1.0

[gnuletik]

A simple PR to upgrade css-loader to version 2.1.0.
There is a bug with version 1.0.0 when importing a font with a hash at the end.

For example:
This CSS

@font-face {
	font-family: "My Font";
	src: url("My Font.svg#Font Name") format("svg");
}

generates this:

@font-face {
	font-family: "My Font";
	src: url("/static/media/My Font.f84c8961.svg"#Font Name) format("svg");
}

(which is invalid)

This issue is fixed in css-loader v2.0.0.
See the changelog here: https://github.com/webpack-contrib/css-loader/blob/master/CHANGELOG.md
In this commit: webpack-contrib/css-loader#803

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[ianschmitz]

I'm not clear whether we would need to release this as a breaking change in CRA as well. The breaking changes can be seen here: https://github.com/webpack-contrib/css-loader/releases/tag/v2.0.0, or how this will affect things like absolute scss file imports that work today.

I'm going to tag this as a breaking change but if somebody else with some more knowledge of this loader feels otherwise then let us know!

[mrmckeb]

@gnuletik, from what we've read, this disables CSS module support by default, and it needs to be enabled in the config. Can you please update this PR to enable that feature?
https://github.com/webpack-contrib/css-loader/blob/master/CHANGELOG.md#features-1

[ianschmitz]

I forgot i had done this as part of #6614. When i was checking the breaking changes i saw that we had already explicitly set modules: true for the css-loader which means we should be good.