Update dependency postcss to v7.0.23

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
postcss (source)	devDependencies	patch	7.0.21 -> 7.0.23

---

Release Notes

postcss/postcss

### [`v7.0.23`](https://togithub.com/postcss/postcss/blob/master/CHANGELOG.md#​7023) [Compare Source](https://togithub.com/postcss/postcss/compare/7.0.22...7.0.23) - Update `Processor#version`. ### [`v7.0.22`](https://togithub.com/postcss/postcss/blob/master/CHANGELOG.md#​7022) [Compare Source](https://togithub.com/postcss/postcss/compare/7.0.21...7.0.22) - Add funding link for `npm fund`.

---

Renovate configuration

:date: Schedule: At any time (no schedule defined).

:vertical_traffic_light: Automerge: Enabled.

:recycle: Rebasing: Whenever PR is stale, or if you modify the PR title to begin with "rebase!".

:no_bell: Ignore: Close this PR and you won't be reminded about this update again.

---

• [ ] If you want to rebase/retry this PR, check this box

---

Newsflash: Renovate has joined WhiteSource, and is now free for all use. Learn more or view updated terms and privacy policies.