Fix config types

packages/netlify-cms-core/index.d.ts

@@ -297,6 +297,7 @@ declare module 'netlify-cms-core' {
 
   export interface CmsCollection {
     name: string;
+    icon?: string;
     label: string;
     label_singular?: string;
     description?: string;

packages/netlify-cms-core/src/types/redux.ts

@@ -603,6 +603,7 @@ export type Format = keyof typeof formatExtensions;
 
 type CollectionObject = {
   name: string;
+  icon?: string;
   folder?: string;
   files?: CollectionFiles;
   fields: EntryFields;