chore: move db-example to examples (#6532)

- Moved to examples
- Removed unnecessary dependencies
- Improved the readme with instructions for writing the db adapter

examples/db-example/src/transactions/commitTransaction.ts

@@ -0,0 +1,14 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
+import type { CommitTransaction } from 'payload/database'
+
+/**
+ * Commits a transaction identified by its ID.
+ *
+ * Optional - this method is not required
+ *
+ * @param {string} id - The ID of the transaction to commit.
+ * @returns {Promise<void>}
+ *
+ * This function is optional and can be implemented as needed for database adapters that support transactions.
+ */
+export const commitTransaction: CommitTransaction = async function commitTransaction(id) {}