https://nodejs.org/api/sqlite.html#databaseapplychangesetchangeset-options
```js
const sourceDb = new DatabaseSync(':memory:');
const targetDb = new DatabaseSync(':memory:');
sourceDb.exec('CREATE TABLE data(key INTEGER PRIMARY KEY, value TEXT)');
targetDb.exec('CREATE TABLE data(key INTEGER PRIMARY KEY, value TEXT)');
const session = sourceDb.createSession();
const insert = sourceDb.prepare('INSERT INTO data (key, value) VALUES (?, ?)');
insert.run(1, 'hello');
insert.run(2, 'world');
const changeset = session.changeset();
targetDb.applyChangeset(changeset);
// Now that the changeset has been applied, targetDb contains the same data as sourceDb.
```
Implements the `readOnly` option for `DatabaseSync`.
Permissions:
`--allow-read=test.db --allow-write=test.db` => all works
`--allow-read=test.db` => only `readOnly` dbs work, cannot create new db
