reimplemented header navbar toggle using redux

src/app/header/header.actions.ts

@@ -0,0 +1,26 @@
+import { Injectable } from "@angular/core";
+import { Action } from "@ngrx/store";
+
+@Injectable()
+export class HeaderActions {
+  static COLLAPSE = 'dspace/header/COLLAPSE';
+  collapse(): Action {
+    return {
+      type: HeaderActions.COLLAPSE
+    }
+  }
+
+  static EXPAND = 'dspace/header/EXPAND';
+  expand(): Action {
+    return {
+      type: HeaderActions.EXPAND
+    }
+  }
+
+  static TOGGLE = 'dspace/header/TOGGLE';
+  toggle(): Action {
+    return {
+      type: HeaderActions.TOGGLE
+    }
+  }
+}