📝 (default.html): update documentation links to point to new URLs

Update the links in the documentation to direct users to the new
release and preview URLs. This change ensures that users are
navigated to the correct and updated resources for the Azure DevOps
Migration Tools, improving the accuracy and reliability of the
documentation.

Author: MrHinsh

docs/_layouts/default.html

@@ -80,11 +80,11 @@
                                 <ul class="list-group">
                                     <li class="list-group-item">
                                         <i class="fas fa-question-circle"></i>
-                                        <a href="{{site.baseurl}}" class="ml-2" target="_blank">v#{GitVersion.SemVer}#</a> (latest)
+                                        <a href="https://nkdagility.com/learn/azure-devops-migration-tools/{{page.url}}" class="ml-2" target="_blank">Release</a>
                                     </li>
                                     <li class="list-group-item">
                                         <i class="fab fa-twitter"></i>
-                                        <a href="{{site.baseurl}}/docs/v15.2.0" class="ml-2" target="_blank">v15.2.0</a> (unsupported)
+                                        <a href="https://preview.nkdagility.com/learn/azure-devops-migration-tools/{{page.url}}" class="ml-2" target="_blank">Preview</a>
                                     </li>
                                 </ul>
                             </li>