[FEATURE]: method `.single()` for select query

### Feature hasn't been suggested before.

- [x] I have verified this feature I'm about to request hasn't been suggested before.

### Describe the enhancement you want to request

Hello Drizzle Team,

I suggest method `.single()`

A method that returns a single row is very useful. as you can see in the image I only want to get a single row from the table. with `.limit(1)` I know for sure that the output has `<= 1` items. but when I access it I have to keep using `results[0]` or shorthand it `const [result] = await db...` however it loses the type feature of typescript because `results[0]` (`result`) is recognized by typescript as `Row` while it can be `undefined`