Feature: Add customisable icons in topology (#193)

* [up] add config for custom images, better js

* [up] use bundler to bundle js

* [fix] remove domcontentloaded since defer is used

* [fix] formatting with black

* [fix] images drf api

* [up] add support for custom icons on additional roles: power panel, power feed, circuit

* [up] optimize topology generation by using `_id` when trying to access pk of related object

* [fix] kebab case instead of slugification

* [fix] use empty queryset in api views & change coord save logic

netbox_topology_views/static_dev/css/app.scss

@@ -1,7 +1,27 @@
 #visgraph {
-    height: 70vh;
-  }
+  height: 70vh;
+}
 
 html[data-netbox-color-mode=dark] #visgraph {
   background-color: #212529;
-}
+}
+
+
+.image-dropdown img {
+  width: 64px;
+  height: 64px;
+}
+
+.image-dropdown-content {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.5rem;
+
+  padding-inline: 0.5rem;
+  width: 50vw;
+  max-width: 32rem;
+
+  > img {
+    cursor: pointer;
+  }
+}