Try: Update and fix lint-style (#5537)

* Update @wordpress packages & lint-staged

* Remove = from lint-style command

* Add defaultSeverity rule and custom-syntax config

package.json

@@ -27,20 +27,24 @@
 	},
 	"devDependencies": {
 		"@octokit/rest": "^18.12.0",
-		"@wordpress/prettier-config": "^1.1.1",
-		"@wordpress/scripts": "^19.2.2",
-		"@wordpress/stylelint-config": "^19.1.0",
+		"@wordpress/prettier-config": "^1.1.2",
+		"@wordpress/scripts": "^21.0.2",
+		"@wordpress/stylelint-config": "^20.0.1",
 		"chokidar-cli": "^3.0.0",
 		"fs-extra": "^10.0.0",
 		"husky": "^7.0.4",
 		"inquirer": "^8.2.0",
-		"lint-staged": "^12.1.7",
+		"lint-staged": "^12.3.4",
 		"lodash": "^4.17.21",
 		"open": "^8.4.0"
 	},
+	"stylelint": {
+		"extends": "@wordpress/stylelint-config",
+		"defaultSeverity": "warning"
+	},
 	"lint-staged": {
 		"*.scss": [
-			"wp-scripts lint-style --fix="
+			"wp-scripts lint-style --fix --custom-syntax postcss-scss"
 		]
 	},
 	"dependencies": {