Update contribution link to point to elastic.co and open in new window

Co-authored-by: theletterf <[email protected]>

Author: Copilot

docs/contribute/on-the-web.md

@@ -3,7 +3,7 @@
 This section will help you understand how to update and contribute to our documentation post-migration.
 
 :::{tip}
-Every documentation page includes a **Learn how to contribute** link in the sidebar that brings you directly to this guide. Use it whenever you want to contribute!
+Every documentation page includes a **Learn how to contribute** link in the sidebar that takes you to the [Elastic Docs contribution guide](https://www.elastic.co/docs/contribute-docs/). Use it whenever you want to contribute!
 :::
 
 ## Updating documentation

src/Elastic.Markdown/Layout/_TableOfContents.cshtml

@@ -35,7 +35,7 @@
 				</li>
 			}
 			<li class="learn-how-to-contribute hidden lg:block lg:not-first:mt-1">
-				<a href="@Model.Link("/contribute/#contribute")" class="link text-sm">
+				<a href="https://www.elastic.co/docs/contribute-docs/" class="link text-sm" target="_blank">
 					Learn how to contribute
 				</a>
 			</li>