Dynamic Loading of PR Events

[mheidinger]

So far statically the first 30 events for a Pull Request are loaded. The user pressing "Load more" just shows the next 5 of those 30 but will never load any more from GitHub.

This behaviour could be improved by only fetching the first e.g. 5 or 10 events of each PR and then dynamically loading the next few events only on the user pressing "Load more".

Reducing the initial load could also benefit #4.

[mheidinger]

Potentially this could also be used to only load new events using the after filter in GraphQL and the last received event.