change IS_DEV check to allow localhost

Author: mozzius

bskyembed/README.md

@@ -23,4 +23,4 @@ In another terminal window, run the snippet dev script:
 yarn dev-snippet
 ```
 
-Then, open `file:/<your files>/social-app/bskyembed/test.html` in your browser.
+You can then see the testbed page at http://localhost:5173/test

bskyembed/snippet/embed.ts

@@ -7,11 +7,13 @@ interface Window {
 }
 
 /**
- * Allow url to be overwritten during development. `file:` protcol check
- * should mean it won't ever get accidentally overridden in production
+ * Allow url to be overwritten during development
  */
+const IS_DEV =
+  window.location.protocol === 'file:' ||
+  window.location.hostname === 'localhost'
 const EMBED_URL =
-  window.location.protocol === 'file:' && window.BSKY_DEV_EMBED_URL
+  IS_DEV && window.BSKY_DEV_EMBED_URL
     ? window.BSKY_DEV_EMBED_URL
     : 'https://embed.bsky.app'