Adds ringing.scss, which was missing

css/ringing/_ringing.scss

+.ringing {
+    display: block;
+    left: 0;
+    top: 0;
+    width: 100%;
+    height: 100%;
+    position: fixed;
+    z-index: $overlayZ;
+    //background: linear-gradient(transparent, #000);
+    background: $defaultBackground; /* Old browsers */
+    opacity: 0.8;
+
+    &__content {
+        position: absolute;
+        width: 400px;
+        height: 250px;
+        left: 50%;
+        top: 50%;
+        margin-left: -200px;
+        margin-top: -125px;
+        font-weight: 400;
+        font-size: 14px;
+        text-align: center;
+    }
+
+    &__avatar {
+        width: 100px;
+        height: 100px;
+        border-radius: 50%;
+    }
+
+    &__caller-info {
+        .mention {
+            color: #333;
+        }
+    }
+}