rename master to main in doc links

Author: dannyvankooten

CHANGELOG.md

@@ -109,7 +109,7 @@ This drops support for some very old browsers, but results in smaller bundle siz
 
 #### 4.9.2 - Mar 21, 2023
 
-- Add support for a field named `MARKETING_PERMISSIONS` to enable GDPR fields configured in Mailchimp. A [sample code snippet can be found here](https://github.com/ibericode/mailchimp-for-wordpress/blob/master/sample-code-snippets/forms/gdpr-marketing-permissions.md).
+- Add support for a field named `MARKETING_PERMISSIONS` to enable GDPR fields configured in Mailchimp. A [sample code snippet can be found here](https://github.com/ibericode/mailchimp-for-wordpress/blob/main/sample-code-snippets/forms/gdpr-marketing-permissions.md).
 - Remove Google reCaptcha feature. This was already disabled if you were not already using it.
 
 

README.md

@@ -63,5 +63,5 @@ If you need priority support, [upgrade to Mailchimp for WordPress Premium](https
 Developers
 ----------
 
-Looking for code snippets? Have a look at the [sample code snippets directory](https://github.com/ibericode/mailchimp-for-wordpress/tree/master/sample-code-snippets) for a collection of modification examples.
+Looking for code snippets? Have a look at the [sample code snippets directory](https://github.com/ibericode/mailchimp-for-wordpress/tree/main/sample-code-snippets) for a collection of modification examples.