docs: support multiple gtag ids

Signed-off-by: Adam Setch <adam.setch@outlook.com>

Author: setchy

src/components/GoogleAnalytics.astro

@@ -1,19 +1,21 @@
 ---
 import { siteMetadata } from '../constants.ts';
 
-const GTAG_ID = siteMetadata.google.gtag;
-const GTAG_SRC = `https://www.googletagmanager.com/gtag/js?id=${GTAG_ID}`;
+const GTAG_IDS = siteMetadata.google.gtags;
+const GTAG_SRC = `https://www.googletagmanager.com/gtag/js?id=${GTAG_IDS[0]}`;
 ---
 
 <!-- Google tag (gtag.js) -->
 <script async src={GTAG_SRC}></script>
-<script define:vars={{ GTAG_ID }}>
+<script define:vars={{ GTAG_IDS }}>
 window.dataLayer = window.dataLayer || [];
 function gtag() {
   // biome-ignore lint/complexity/noArguments: keep arguments object as per gtag.js spec
   dataLayer.push(arguments);
 }
 gtag('js', new Date());
 
-gtag('config', GTAG_ID);
+GTAG_IDS.forEach((gtagId) => {
+  gtag('config', gtagId);
+});
 </script>

src/constants.ts

@@ -13,7 +13,7 @@ export const siteMetadata = {
     site: 'https://setchy.io',
   },
   google: {
-    gtag: 'G-736BKHY5WS',
+    gtags: ['G-736BKHY5WS'],
     siteVerification: '',
   },
   menuLinks: [