feat: Add fieldtype icon fix and smart field auto-discovery in config panel

- Fix fieldtype icon not rendering in blueprint editor by using the
  correct 'fieldtype-entries' icon identifier
- Add a new ReverseRelationshipFieldSelect hidden fieldtype and Vue
  component that auto-discovers relationship fields from the selected
  collection/taxonomy/container via a CP API endpoint
- The field selector polls for sibling config changes so switching
  collections instantly refreshes the available fields
- Auto-selects the field handle when only one relationship field exists
- Update README credits

Author: sylvesterdamgaard

README.md

@@ -1,6 +1,6 @@
 {
   "resources/js/addon.js": {
-    "file": "assets/addon-DM8RGZn0.js",
+    "file": "assets/addon-DMIVz1vC.js",
     "name": "addon",
     "src": "resources/js/addon.js",
     "isEntry": true

resources/dist/build/assets/addon-DM8RGZn0.js

@@ -1,5 +1,7 @@
 import ReverseRelationship from './components/fieldtypes/ReverseRelationship.vue'
+import ReverseRelationshipFieldSelect from './components/fieldtypes/ReverseRelationshipFieldSelect.vue'
 
 Statamic.booting(() => {
     Statamic.$components.register('reverse_relationship-fieldtype', ReverseRelationship)
+    Statamic.$components.register('reverse_relationship_field_select-fieldtype', ReverseRelationshipFieldSelect)
 });