index.html: use variables where possible

index.html

@@ -119,12 +119,12 @@ robots: noai, nofollow
     >
     <small
       ><a
-        href="https://www.facebook.com/profile.php?id=61560831284680"
+        href="https://www.facebook.com/profile.php?id={{ site.facebook_username }}"
         rel="me"
         >facebook</a
       >
       (<a
-        href="http://facebookwkhpilnemxj7asaniu7vnjjbiltxjqhye3mhbshg7kx5tfyd.onion/profile.php?id=61560831284680"
+        href="http://facebookwkhpilnemxj7asaniu7vnjjbiltxjqhye3mhbshg7kx5tfyd.onion/profile.php?id={{ site.facebook_username }}"
         rel="me"
         >&#129477;&#65038;</a
       >)</small
@@ -152,7 +152,7 @@ robots: noai, nofollow
     >)
     <small
       ><a
-        href="https://www.instagram.com/amiauh39/"
+        href="https://www.instagram.com/{{ site.instagram_username }}/"
         rel="me"
         >Instagram</a
       ></small
@@ -186,8 +186,8 @@ robots: noai, nofollow
     <a
       rel="me"
       type="application/activity+json"
-      href="https://sauna.social/users/aminda"
+      href="https://{{ site.mastodon.instance }}/users/{{ site.mastodon.username }}"
-      >sauna.social</a
+      >{{site.mastodon.instance}}</a
     >
   </li>
   <li