Rename PostCSS files to .pcss (#22769)

* Rename PostCSS files to `.pcss`

* Make Stylelint happy

* Make Stylelint happy v2

* Update CompatibilityView.tsx

* Update res/css/structures/ErrorView.pcss

Co-authored-by: Michael Weimann <mail@michael-weimann.eu>

* Merge branch 'develop' of github.com:matrix-org/matrix-react-sdk into t3chguy/pcss


 Conflicts:

	package.json

	res/css/_components.scss

	res/css/structures/_NotificationPanel.pcss

	res/css/views/dialogs/_SpotlightDialog.pcss

	res/css/views/rooms/_EventTile.pcss

	res/css/views/rooms/_ReadReceiptGroup.pcss

	yarn.lock

* Only use CI_PACKAGE mode on develop, it skips minification which can find some errors

* Keep name to not break existing PRs

Co-authored-by: Michael Weimann <mail@michael-weimann.eu>

src/vector/jitsi/index.ts

@@ -29,7 +29,7 @@ import { SnakedObject } from "matrix-react-sdk/src/utils/SnakedObject";
 import { getVectorConfig } from "../getconfig";
 
 // We have to trick webpack into loading our CSS for us.
-require("./index.scss");
+require("./index.pcss");
 
 const JITSI_OPENIDTOKEN_JWT_AUTH = 'openidtoken-jwt';