Added Substack

Added Substack CSS branding and icon.

css/brands.css

@@ -571,6 +571,16 @@ button:hover,
   filter: brightness(90%);
 }
 
+/* Substack */
+.button.button-substack {
+  color: #ffffff;
+  background-color: #FF6719;
+}
+.button.button-substack:hover,
+.button.button-substack:focus {
+  filter: brightness(90%);
+}
+
 /* Telegram */
 .button.button-telegram {
   color: #ffffff;

images/icons/substack.svg

@@ -0,0 +1,3 @@
+<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M22.539 8.242H1.45999V5.406H22.54V8.242H22.539ZM1.45999 10.812V24L12 18.11L22.54 24V10.812H1.45999ZM22.54 0H1.45999V2.836H22.54V0Z" fill="white"/>
+</svg>

index.html

@@ -196,6 +196,11 @@
             <img class="icon" src="images/icons/google-podcasts.svg" alt="Google Podcasts Logo">Listen on Google Podcasts</a>
         <br>
 
+        <!-- Clubhouse -->
+        <a class="button button-substack" href="#" target="_blank" rel="noopener">
+            <img class="icon" src="images/icons/substack.svg" alt="Substack Logo">Subscribe on Substack</a>
+        <br>
+
         <!-- Clubhouse -->
         <a class="button button-clubhouse" href="#" target="_blank" rel="noopener">
             <img class="icon" src="images/icons/clubhouse.svg" alt="Clubhouse Logo">Clubhouse</a>