triage

This was in an older version before my refactor, but the idea is you quickly walk through your notifications, assign a priority, and later list them by the global priority across all projects. This will be handy when you have dozens or hundreds of projects. Later it'd also be nice to integrate with GH Sponsors. [x] add user configuration for the priorities [x] add priority selection page [x] create labels if they're not present [x] remove others when selecting a new priority [x] filter priority labels from label listing [x] add issues page sorted by priority [ ] add some kind of tab system to indicate which top-level page you're on [ ] make as read after assigning priority [ ] fetch issues by priority label(s) [ ] list them [ ] add the same filtering with [ ] decide on default shortcuts for switching tabs [ ] docs