replace special chars when building the RegEexp object (cf. #214)

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

@@ -1691,7 +1691,7 @@ this.singlefile.lib.core = this.singlefile.lib.core || (() => {
 		}
 
 		static async evalTemplateVariable(template, variableName, valueGetter, dontReplaceSlash, replacementCharacter) {
-			const replaceRegExp = new RegExp("{\\s*" + variableName + "\\s*}", "g");
+			const replaceRegExp = new RegExp("{\\s*" + variableName.replace(/\W|_/g, "[$&]") + "\\s*}", "g");
 			if (template && template.match(replaceRegExp)) {
 				let value = await valueGetter();
 				if (!dontReplaceSlash) {