Update dependency purgecss-webpack-plugin to v5

This MR contains the following updates:

Package	Type	Update	Change
purgecss-webpack-plugin (source)	dependencies	major	4.1.3 -> 5.0.0

---

Release Notes

FullHuman/purgecss

v5.0.0

Compare Source

Bug Fixes

• add safelist variables to postcss-purgecss #​840 (c822058)
• gulp-purgecss: support skippedContentGlobs option #​853 (b72de77)
• Purgecss webpack plugin/only filter fix (#​933) (f8e4c2c)
• purgecss-webpack-plugin: add sourcemap support #​409 (b3f73ed)
• purgecss-webpack-plugin: export as named export as well as default (#​821) (a6a2c8e)
• wrong path import (4f3ddd0)

Features

• add source map support #​526 (f2a9c5a)
• gulp-purgecss: add support for gulp-sourcemaps #​257 (55c26d2)
• postcss-purgecss: load options from purgecss config (4de3bd8)
• purgecss-webpack-plugin: load config file automatically #​767 (726faaa)

BREAKING CHANGES

• purgecss-webpack-plugin: drop webpack 4 support

---

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

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

♻ Rebasing: Whenever MR becomes conflicted, 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.