Additional column for conferences

Currently we support only hackathons, but based on members feedback we could also support additional space for conferences. We could create additional column for storing these.

1. We could reuse some logic from `HackathonsCollector`
```jsx

Incoming hackathons:

```
and provide similar sections - "Incoming conferences" and "Previous conferences" and place it below hackathons

2. Filters logic could be generalised to functions that takes array of events (if we preserve the same json structure)