Add canvas previews, external extension links, and release notes showcase (#1987)

* Add extension thumbnails and preview assets

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add clickable extension image preview modal

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address PR review feedback

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update website/src/styles/global.css

* Add preview assets for canvas extensions

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update canvas extension preview images

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Delete extensions/backlog-swipe-triage/assets/swipe-canvas-triage.png

* Support external canvas extensions and add Coffilot

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add homepage link to GitHub repository

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add release notes showcase canvas extension

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Enhance release notes canvas sourcing and layout

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Aaron Powell <me@aaron-powell.com>

website/src/pages/index.astro

@@ -40,6 +40,11 @@ const base = import.meta.env.BASE_URL;
           Community-contributed agents, instructions, and skills to enhance your
           GitHub Copilot experience
         </p>
+        <p>
+          <a href="https://github.com/github/awesome-copilot/" target="_blank" rel="noopener noreferrer">
+            View the Awesome Copilot repository on GitHub
+          </a>
+        </p>
       </div>
     </section>