Fx147: Add relnote for iterator sequencing support (mdn#42713)

add update for iterator sequencing

Author: dipikabh

files/en-us/mozilla/firefox/releases/147/index.md

@@ -62,6 +62,8 @@ Firefox 147 is the current [Beta version of Firefox](https://www.firefox.com/en-
 
 - CSS module scripts are now supported, allowing a stylesheet to be loaded into a script as a {{domxref("CSSStyleSheet")}} instance using the [`import`](/en-US/docs/Web/JavaScript/Reference/Statements/import) keyword and the [`type` import attribute](/en-US/docs/Web/JavaScript/Reference/Statements/import/with) set to `type="css"`.
   ([Firefox bug 1986681](https://bugzil.la/1986681)).
+- The {{jsxref("Iterator.concat()")}} method is now supported. This method enables you to create a new iterator that combines multiple input iterables into a single sequence.
+  ([Firefox bug 1986672](https://bugzil.la/1986672)).
 
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