Clean up package.json and update libraries (#781)

Author: t-hamano

.stylelintrc.json

@@ -1,11 +1,10 @@
 {
-	"extends": "@wordpress/stylelint-config/scss",
+	"extends": "@wordpress/stylelint-config/scss-stylistic",
 	"rules": {
 		"at-rule-empty-line-before": null,
 		"at-rule-no-unknown": null,
 		"comment-empty-line-before": null,
 		"font-weight-notation": null,
-		"max-line-length": null,
 		"no-descending-specificity": null,
 		"rule-empty-line-before": null,
 		"selector-class-pattern": null,