Fix unescaped attr value in generated CSS selector

Related feedback:
- NanoAdblocker/NanoCore2@5e625da8fe45#commitcomment-36625096

src/js/contentscript.js

@@ -952,7 +952,7 @@ vAPI.domCollapser = (function() {
             if ( netSelectorCacheCount <= netSelectorCacheCountMax ) {
                 const value = target.getAttribute(prop);
                 if ( value ) {
-                    selectors.push(tag + '[' + prop + '="' + value + '"]');
+                    selectors.push(`${tag}[${prop}="${CSS.escape(value)}"]`);
                     netSelectorCacheCount += 1;
                 }
             }