✨ Implement newsletter subscription form using API

Switch from SendInBlue to EmailOctopus for newsletter. Now uses their API through the form to handle subscription.

src/style/organisms/_newsletter.scss

@@ -46,6 +46,21 @@
         }
     }
 
+    // Form input
+    :global(.newsletter-form__email) {
+        :global(input) {
+            color: $color-text;
+        }
+        :global(input::placeholder) {
+            color: $color-gray;
+        }
+    }
+    // Form message
+    :global(.newsletter-form__message.is-success) {
+        color: #fff;
+        background: $color-primary-tertiary20;
+    }
+
 
     /*
     ** Variants
@@ -56,10 +71,6 @@
 
         :global(.newsletter-form__email) {
             background: $color-tertiary;
-
-            :global(input::placeholder) {
-                color: $color-gray;
-            }
         }
      }
     // Light