Fix/menu (CenterForOpenScience#262)

* fix(menu): added new items

* fix(menu): updated naming

* fix(menu): changed overview to discover and replaced some icons

* fix(menu): added margin

* fix(menu): fixed links to discover

Author: nsemets

src/app/core/constants/nav-items.constant.ts

@@ -235,7 +235,7 @@ export const MENU_ITEMS: MenuItem[] = [
     items: [
       {
         id: 'registries-overview',
-        routerLink: '/registries/overview',
+        routerLink: '/registries/discover',
         label: 'navigation.discover',
         visible: true,
         routerLinkActiveOptions: { exact: true },
@@ -266,7 +266,7 @@ export const MENU_ITEMS: MenuItem[] = [
     items: [
       {
         id: 'preprints-overview',
-        routerLink: '/preprints/overview',
+        routerLink: '/preprints/discover',
         label: 'navigation.discover',
         visible: true,
         routerLinkActiveOptions: { exact: false },