Add read more link

Author: bomsy

README.md

@@ -240,9 +240,9 @@ following attributes:
 
 - `file`: Optional. The generated filename this source map is associated with.
 
-- `x_google_ignoreList`: Optional. An additional extension field which is an array 
-of indices refering to urls in the sources array. This is used to identify third-party
-sources, that the developer might want to avoid when debugging.
+- `x_google_ignoreList`: Optional. An additional extension field which is an array
+  of indices refering to urls in the sources array. This is used to identify third-party
+  sources, that the developer might want to avoid when debugging. [Read more](https://developer.chrome.com/articles/x-google-ignore-list/)
 
 The promise of the constructed souce map consumer is returned.