feat: Add CalendarSelector component and install new dependencies.

node_modules/concurrently/index.d.ts

@@ -0,0 +1,11 @@
+/*
+ * While in local development, make sure you've run `pnpm run build` first.
+ */
+import { concurrently } from './dist/src/index.js';
+
+export * from './dist/src/index.js';
+// @ts-expect-error ignore the usage of `export =` along with `export default`.
+// This is seemingly fine, but the file needs to be included in the TS project, which can't be done
+// due to importing from `dist`. See https://stackoverflow.com/q/42609768/2083599
+export = concurrently;
+export default concurrently;