PLT-2553 Additional backstage UI Improvements (#2673)

* Renamed Commands to Slash Commands in backstage UI

* Updated displayed info for listed commands and outgoing webhooks

* Disallowed empty outgoing webhook trigger words and improved client-side validation for them

webapp/sass/routes/_backstage.scss

@@ -192,6 +192,7 @@ body {
     }
 
     .item-details {
+        color: $dark-gray;
         flex-grow: 1;
         flex-shrink: 1;
         overflow: hidden;
@@ -204,6 +205,7 @@ body {
     }
 
     .item-details__name {
+        color: black;
         font-weight: 600;
     }
 
@@ -213,8 +215,8 @@ body {
 
     .item-details__description,
     .item-details__token,
+    .item-details__trigger-words,
     .item-details__creation {
-        color: $dark-gray;
         display: inline-block;
         margin-top: 10px;
         vertical-align: top;
@@ -224,6 +226,10 @@ body {
         }
     }
 
+    .item-details__trigger-words {
+        white-space: nowrap;
+    }
+
     .item-actions {
         flex-grow: 0;
         flex-shrink: 0;