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/js/csrftoken.js

@@ -0,0 +1,17 @@
+export const getCookie = (name) => {
+    if (!document.cookie) return
+
+    let cookieValue = null
+    const cookies = document.cookie.split(';')
+
+    for (let i = 0; i < cookies.length; i++) {
+        const cookie = cookies[i].trim()
+        // Does this cookie string begin with the name we want?
+        if (cookie.substring(0, name.length + 1) === name + '=') {
+            cookieValue = decodeURIComponent(cookie.substring(name.length + 1))
+            break
+        }
+    }
+
+    return cookieValue
+}