Washington, DC events scraper

### Feature Description

_A clear and concise description of the feature you're requesting._

Provide a file in `cdp_scrapers/instances/` like `cdp_scrapers/instances/dc.py` or something similar that provides a function that implements API to return Washington, DC city council meetings as `List[EventIngestionModel]` for a period of time, e.g.

```Python
get_events(begin: Optional[datetime] = None, end: Optional[datetime] = None) -> List[EventIngestionModel]
```

### Use Case

_Please provide a use case to help us understand your request in context._

Above file and API would be used in deploying a CDP instance for Washington, DC.

Start by reviewing the existing files in cdp_scrapers/instances/ and the EventIngestionModel API, then identify how those scrapers expose get_events with date bounds. The work is done when a Washington, DC instance provides that function and returns city council meetings as List[EventIngestionModel] for the requested period.

Written by the indexing model from the issue text.