Added AddIntegration page

webapp/sass/routes/_backstage.scss

@@ -92,7 +92,7 @@
     max-width: 958px;
 }
 
-.installed-integrations__header {
+.backstage__header {
     margin-bottom: 20px;
     width: 100%;
 
@@ -180,3 +180,33 @@
         padding-left: 20px;
     }
 }
+
+.add-integration-option {
+    background-color: white;
+    border: lightgray 1px solid;
+    display: inline-block;
+    height: 210px;
+    margin-right: 30px;
+    padding: 20px;
+    text-align: center;
+    width: 250px;
+
+    &:hover {
+        color: default;
+        text-decoration: none;
+    }
+
+    &__image {
+        width: 80px;
+        height: 80px;
+    }
+
+    &__title {
+        color: black;
+        margin-bottom: 10px;
+    }
+
+    &__description {
+        color: gray;
+    }
+}