chore: Amended site: links in diataxis cards

docs/cards/diataxis/cards.yml

 - title: |
-    [Tutorials](site:tutorials/index.html)
+    [Tutorials](site:tutorials)
   content: |
     <img class="dtx" src="site:cards/diataxis/img/tutorials.jpg" alt="Tutorials">
     <a href="https://diataxis.fr/tutorials/">
@@ -14,7 +14,7 @@
     <h6 class="dtx">e.g. <i>"How do I add automated releasing to my Python library?"</i></h6>
 
 - title: |
-    [How-To's](site:howtos/index.html)
+    [How-To's](site:howtos)
   content: |
     <img class="dtx" src="site:cards/diataxis/img/howtos.jpg" alt="How-To's">
     <a href="https://diataxis.fr/how-to-guides/">
@@ -29,7 +29,7 @@
     <h6 class="dtx">e.g. <i>"Walk me through making a new Python library?"</i></h6>
 
 - title: |
-    [Explanations](site:explanations/index.html)
+    [Explanations](site:explanations)
   content: |
     <img class="dtx" src="site:cards/diataxis/img/explanations.jpg" alt="Explanations">
     <a href="https://diataxis.fr/explanation/">
@@ -44,7 +44,7 @@
     <h6 class="dtx">e.g. <i>"Why do we use Poetry for packaging?"</i></h6>
 
 - title: |
-    [Reference](site:reference/index.html)
+    [Reference](site:reference)
   content: |
     <img class="dtx" src="site:cards/diataxis/img/reference.png" alt="Reference">
     <a href="https://diataxis.fr/reference/">