chore(deps): update dependency postcss-loader to v6

This MR contains the following updates:

Package	Type	Update	Change
postcss-loader	devDependencies	major	4.3.0 -> 6.1.0

---

Release Notes

webpack-contrib/postcss-loader

v6.1.0

Compare Source

v6.0.0

Compare Source

v5.3.0

Compare Source

v5.2.0

Compare Source

v5.1.0

Compare Source

v5.0.0

Compare Source

---

Configuration

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

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever MR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box.

---

This MR has been generated by Renovate Bot.