Revert "Add yet-another-react-lightbox package and update .gitignore to exclude node_modules"

This reverts commit c92f4a5edd.

frontend/node_modules/@fullcalendar/core/preact.d.ts

@@ -0,0 +1,8 @@
+import * as preact from 'preact';
+export * from 'preact';
+export { createPortal } from 'preact/compat';
+
+declare function flushSync(runBeforeFlush: any): void;
+declare function createContext<T>(defaultValue: T): preact.Context<T>;
+
+export { createContext, flushSync };