Can't create a connection pool when running the example from the README

### Describe the bug

For some reason, running your example runs into a NotImplementedError of asyncio when it tries to create a connection pool. The PostgreSQL psycopg2 package works just fine when I use it directly without aiopg.

### To Reproduce

As already said, the code is just the first example of the README with the dsn modified to connect to my database.

```py
import asyncio
import aiopg

dsn = ...

async def go():
async with aiopg.create_pool(dsn) as pool:
async with pool.acquire() as conn:
async with conn.cursor() as cur:
await cur.execute("SELECT 1")
ret = []
async for row in cur:
ret.append(row)
assert ret == [(1,)]

loop = asyncio.get_event_loop()
loop.run_until_complete(go())
```

Running the example with psycopg2 works just fine.

```py
import psycopg2

dsn = ...

conn = psycopg2.connect(dsn=dsn)
cursor = conn.cursor()
cursor.execute("SELECT 1")
rows = cursor.fetchall() # contains [(1,)] as expected
cursor.close()
conn.close()
```

I've tried both Python 3.11 and 3.12, but still same error. I even downgraded to Python 3.11 as I've seen you don't support 3.12 yet.

``python -m pip list`` for my 3.11 environment yields

```txt
Package Version
---------------- -----------
aiofiles 24.1.0
aiohappyeyeballs 2.4.0
aiohttp 3.10.5
aiopg 1.4.0
aiosignal 1.3.1
async-timeout 4.0.3
attrs 24.2.0
colorama 0.4.6
frozenlist 1.4.1
idna 3.7
multidict 6.0.5
numpy 1.26.4
pandas 2.2.0
pip 24.2
psycopg2-binary 2.9.9
python-dateutil 2.9.0.post0
pytz 2024.1
six 1.16.0
tqdm 4.66.2
tzdata 2024.1
yarl 1.9.4
```

### Expected behavior

Same result as in the example. Assertion passes.

### Logs/tracebacks

```python-traceback
Traceback (most recent call last):
File "C:\Users\mtroester\source\repos\kfz_webapi_migration\aiopg_test.py", line 22, in
loop.run_until_complete(go())
File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2544.0_x64__qbz5n2kfra8p0\Lib\asyncio\base_events.py", line 654, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "C:\Users\mtroester\source\repos\kfz_webapi_migration\aiopg_test.py", line 12, in go
async with aiopg.create_pool(dsn) as pool:
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\utils.py", line 82, in __aenter__
self._obj = await self._coro
^^^^^^^^^^^^^^^^
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\pool.py", line 300, in from_pool_fill
await self._fill_free_pool(False)
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\pool.py", line 336, in _fill_free_pool
conn = await connect(
^^^^^^^^
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\connection.py", line 65, in connect
connection = Connection(
^^^^^^^^^^^
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\connection.py", line 772, in __init__
self._loop.add_reader(
File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2544.0_x64__qbz5n2kfra8p0\Lib\asyncio\events.py", line 534, in add_reader
raise NotImplementedError
NotImplementedError
Exception ignored in:
Traceback (most recent call last):
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\connection.py", line 1188, in __del__
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\connection.py", line 995, in close
File "C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\aiopg\connection.py", line 977, in _close
File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.11_3.11.2544.0_x64__qbz5n2kfra8p0\Lib\asyncio\events.py", line 537, in remove_reader
NotImplementedError:
```

### Python Version

```console
$ python --version
Python 3.11.9

(it's the official Python 3.11 version installed by the Windows 11 App Store)
```

### aiopg Version

```console
$ python -m pip show aiopg
Name: aiopg
Version: 1.4.0
Summary: Postgres integration with asyncio.
Home-page: https://aiopg.readthedocs.io
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: BSD
Location: C:\Users\mtroester\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages
Requires: async-timeout, psycopg2-binary
Required-by:
```

### OS

Windows 11 Pro
Version 23H2

### Additional context

I'm not sure whether I'm using the correct package versions together. When your base example doesn't work anymore, that's a huge deal IMO.

### Code of Conduct

- [X] I agree to follow the aio-libs Code of Conduct