create AdminSchedulePostingPage placeholder (#223)

frontend/src/App.tsx

@@ -46,6 +46,7 @@ import AdminPostingDetails from "./components/pages/admin/posting/AdminPostingDe
 import customTheme from "./theme";
 import { AuthenticatedUser } from "./types/AuthTypes";
 import VolunteerShiftsPage from "./components/pages/volunteer/shift/VolunteerShiftsPage";
+import AdminSchedulePostingPage from "./components/pages/admin/schedule/AdminSchedulePostingPage";
 
 const App = (): React.ReactElement => {
   const currentUser: AuthenticatedUser = getLocalStorageObj<AuthenticatedUser>(
@@ -161,6 +162,11 @@ const App = (): React.ReactElement => {
                       path={Routes.ADMIN_POSTING_DETAILS}
                       component={AdminPostingDetails}
                     />
+                    <PrivateRoute
+                      exact
+                      path={Routes.ADMIN_SCHEDULE_POSTING_PAGE}
+                      component={AdminSchedulePostingPage}
+                    />
                     <PrivateRoute
                       exact
                       path={Routes.NOT_FOUND_PAGE}

frontend/src/components/pages/admin/schedule/AdminSchedulePostingPage.tsx

@@ -0,0 +1,25 @@
+import { Flex, Text, VStack } from "@chakra-ui/react";
+import React from "react";
+
+import { useParams } from "react-router-dom";
+
+const AdminSchedulePostingPage = (): React.ReactElement => {
+  const { id } = useParams<{ id: string }>();
+
+  return (
+    <Flex
+      flexDir="column"
+      width="100%"
+      height="100vh"
+      justifyContent="center"
+      alignItems="center"
+    >
+      <VStack spacing={4}>
+        <Text>Hello! 👋 This is a placeholder page.</Text>
+        <Text>The id is: {id}</Text>
+      </VStack>
+    </Flex>
+  );
+};
+
+export default AdminSchedulePostingPage;

frontend/src/constants/Routes.ts

@@ -34,3 +34,5 @@ export const ADMIN_POSTING_CREATE_REVIEW_PAGE = "/admin/posting/create/review";
 export const VOLUNTEER_POSTING_DETAILS = "/volunteer/posting/:id";
 
 export const ADMIN_POSTING_DETAILS = "/admin/posting/:id";
+
+export const ADMIN_SCHEDULE_POSTING_PAGE = "/admin/schedule/posting/:id";