[DOCS] Fix LinkServiceHook changelog

Add a missing semicolon and a comment to
a code example.

Resolves: #94933
Releases: master, 10.4
Change-Id: I0c028b72e111591cdd8ac33e76d7aaff18543363
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70686


Tested-by: Henrik Elsner <helsner@dfau.de>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Henrik Elsner <helsner@dfau.de>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>

typo3/sysext/core/Documentation/Changelog/8.7.x/Important-79647-AddedHookForResolvingCustomLinkTypes.rst

@@ -41,7 +41,8 @@ An example implementation for custom links that use `myLinkIdentifier:` as a pre
             return;
          }
 
-         $parameters['result'] = ['myLinkIdentifier' => substr($parameters['urn'], 17)]
+         // Be aware: substr of 17 because of the identifier and the colon
+         $parameters['result'] = ['myLinkIdentifier' => substr($parameters['urn'], 17)];
          $parameters['result']['type'] = 'myLinkIdentifier';
       }
    }