feat(added button placeholders for top-component): added button placeholders for top bar component

src/components/FunctionalArea/TopBar/TopBar.component.tsx

 import { SearchBar } from '@/components/FunctionalArea/TopBar/SearchBar';
 import { UserAvatar } from '@/components/FunctionalArea/TopBar/UserAvatar';
+import { Button } from '@/shared/Button';
 
 export const TopBar = (): JSX.Element => (
   <div className="w-100 bg-white h-16 flex flex-row items-center py-4 pl-7 pr-6 justify-between">
     <div className="flex flex-row items-center">
       <UserAvatar />
       <SearchBar />
+      <Button icon="plus" isIcon isFrontIcon className="ml-8 mr-4">
+        Submaps
+      </Button>
+      <Button icon="plus" isIcon isFrontIcon>
+        Overlays
+      </Button>
     </div>
     <div className="bg-primary-100 px-4 py-1 leading-6 text-xs text-primary-500">
       Parkinson disease map