to_sql return inserted row count or list
Potential feature, could `df.to_sql()` return the indexes of the inserted rows? Something like [knex.js Query Builder](https://knexjs.org/#Builder-insert)

```python
inserted = df.to_sql(con=engine, name=example_table, if_exists='replace', index=False)
```
#### Problem description
This would allow for more quickly knowing how many rows have been entered from your dataframe

#### Expected Output
Something like `inserted = 2` if 2 rows have been added. Even better would be `inserted = [24, 25]` where inserted is now a list of the inserted primary keys