Add interrelationship icon (#15149)

* Add interrelationship icon

* Fix arrow for rtl

* Fix to predefined color

app/javascript/styles/mastodon/widgets.scss

@@ -446,6 +446,26 @@
     vertical-align: initial !important;
   }
 
+  &__interrelationships {
+    width: 21px;
+  }
+
+  .fa {
+    font-size: 16px;
+
+    &.active {
+      color: $highlight-text-color;
+    }
+
+    &.passive {
+      color: $passive-text-color;
+    }
+
+    &.active.passive {
+      color: $active-passive-text-color;
+    }
+  }
+
   @media screen and (max-width: $no-gap-breakpoint) {
     tbody td.optional {
       display: none;