starters: upgrade second-brain, markdown-slides

Renamed Notes starter -> second-brain

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -10,7 +10,7 @@ body:
     options:
     - label: I have [searched](https://github.com/wowchemy/wowchemy-hugo-themes/issues?q=is%3Aissue) for duplicate or closed feature requests
       required: true
-    - label: I am mindful of the project [scope](https://github.com/wowchemy/wowchemy-hugo-themes/blob/main/.github/contributing.md#scope)
+    - label: I am mindful of the project [scope](https://github.com/wowchemy/wowchemy-hugo-themes/blob/main/CONTRIBUTING.md#scope)
       required: true
 - type: textarea
   id: proposal