added "placeholder" in the list of ignored pseudo elements

lib/single-file/modules/css-matched-rules.js

@@ -23,7 +23,7 @@
 this.matchedRules = this.matchedRules || (() => {
 
 	const MEDIA_ALL = "all";
-	const IGNORED_PSEUDO_ELEMENTS = ["after", "before", "first-letter", "first-line", "selection"];
+	const IGNORED_PSEUDO_ELEMENTS = ["after", "before", "first-letter", "first-line", "placeholder", "selection"];
 	const REGEXP_VENDOR_IDENTIFIER = /-(ms|webkit|moz|o)-/;
 	const DEBUG = false;