Customize category prompts through the .toml configuration file.

I forked this repository and intended to implement custom reminders for categories through the following modifications, but an error occurred in the "Run tests" stage of Github Action.

```
D:\a\_temp\a36ab23e-0012-4baa-939f-a3b63fe4030f.sh: line 1: venv/bin/activate: No such file or directory
poetry run aw-notify --help # Ensures that it at least starts
Usage: aw-notify [OPTIONS] COMMAND [ARGS]...

Options:
-v, --verbose Verbose logging.
--testing Enables testing mode.
--help Show this message and exit.

Commands:
checkin Send a summary notification.
start Start the notification service.
make typecheck
make[1]: Entering directory 'D:/a/aw-notify/aw-notify'
poetry run mypy aw_notify --ignore-missing-imports
aw_notify\main.py:307: error: Item "Item" of "Item | Container" has no attribute "__iter__" (not iterable) [union-attr]
aw_notify\main.py:308: error: Invalid index type "str" for "str"; expected type "SupportsIndex | slice[Any, Any, Any]" [index]
aw_notify\main.py:309: error: Invalid index type "str" for "str"; expected type "SupportsIndex | slice[Any, Any, Any]" [index]
aw_notify\main.py:310: error: Item "str" of "Any | str" has no attribute "get" [union-attr]
aw_notify\main.py:311: error: Item "str" of "Any | str" has no attribute "get" [union-attr]
Found 5 errors in 1 file (checked 3 source files)
make[1]: *** [Makefile:11: typecheck] Error 1
make[1]: Leaving directory 'D:/a/aw-notify/aw-notify'
make: *** [Makefile:8: test] Error 2
```

---

`config.toml`

```python
[[alerts]]
category = "All"
thresholds = ["1:00:00", "2:00:00", "4:00:00", "6:00:00", "8:00:00"]
label = "All"

[[alerts]]
category = "Twitter"
thresholds = ["0:15:00", "0:30:00", "1:00:00"]
label = "🐦 Twitter"

[[alerts]]
category = "Youtube"
thresholds = ["0:15:00", "0:30:00", "1:00:00"]
label = "📺 Youtube"

[[alerts]]
category = "Work"
thresholds = ["0:15:00", "0:30:00", "1:00:00", "2:00:00", "4:00:00"]
label = "💼 Work"
positive = true
```

Added Python code

```python
import toml
from datetime import timedelta

def load_alerts_from_config(file_path: str) -> list[CategoryAlert]:
"""从 TOML 文件加载警报配置。"""
config = toml.load(file_path)

alerts = []
for alert_config in config.get('alerts', []):
category = alert_config['category']
thresholds = [timedelta(hours=int(th.split(':')[0]), minutes=int(th.split(':')[1]), seconds=int(th.split(':')[2])) for th in alert_config['thresholds']]
label = alert_config.get('label', category)
positive = alert_config.get('positive', False)

alerts.append(CategoryAlert(category, thresholds, label, positive))

return alerts

def threshold_alerts():
"""
检查每个类别的已用时间，并在达到阈值时触发警报。
"""
# 从配置文件加载警报
alerts = load_alerts_from_config('config.toml')

# 遍历一次以检查是否达到任何阈值
for alert in alerts:
alert.update()
alert.check(silent=True)

while True:
for alert in alerts:
alert.update()
alert.check()
status = alert.status()
if status != getattr(alert, "last_status", None):
logger.debug(f"新状态: {status}")
setattr(alert, "last_status", status)

# TODO: 使其可配置，可能增加默认值以节省资源
sleep(10)
```