moved regexp definition

lib/single-file/single-file-core.js

@@ -995,6 +995,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 	const REGEXP_IMPORT_SIMPLE_QUOTES_FN = /@import\s*'(.*?)'\s*(.*?)(;|$|})/i;
 	const REGEXP_IMPORT_DOUBLE_QUOTES_FN = /@import\s*"(.*?)"\s*(.*?)(;|$|})/i;
 	const REGEXP_IMPORT_NO_QUOTES_FN = /@import\s*(.*?)\s*(.*?)(;|$|})/i;
+	const REGEXP_ESCAPE = /([{}()^$&.*?/+|[\\\\]|\]|-)/g;
 
 	class DomUtil {
 		static normalizeURL(url) {
@@ -1006,7 +1007,7 @@ this.SingleFileCore = this.SingleFileCore || (() => {
 		}
 
 		static getRegExp(string) {
-			return new RegExp(string.replace(/([{}()^$&.*?/+|[\\\\]|\]|-)/g, "\\$1"), "gi");
+			return new RegExp(string.replace(REGEXP_ESCAPE, "\\$1"), "gi");
 		}
 
 		static getUrlFunctions(stylesheetContent) {