Update dependency autoprefixer to v10

Created by: renovate[bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
autoprefixer	^9.8.6 -> ^10.0.4

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Release Notes

postcss/autoprefixer

v10.0.4

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• Fixed Cannot read property 'proxyOf' of undefined error (by Igor Kamyshev).

v10.0.3

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• Fixed substract to subtract value for mask-composite (by Michelle Enos).

v10.0.2

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• Removed -ms-user-select: all because IE and old Edge don’t support it.
• Fixed Grid Layout warning.

v10.0.1

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• Fix PostCSS 8.1 compatability.
• Add our OpenCollective to package.json.
• Clean up code (by Sukka).

v10.0.0

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Autoprefixer 10 is based on top of PostCSS 8 (check Known Issues section before updating).

Node.js 6.x, 8.x, 11.x support was removed.

Now you need to install Autoprefixer by npm install --save-dev autoprefixer postcss. We moved postcss from dependencies to peerDependencies according to new PostCSS plugin guidelines.

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