Support categories on catalog types (#128)

Categories are an optional way of organising your catalog.

Example diff:
```
  ✔ Custom["DocsTeam"] (id=01HSTDDA8AAPGNVYFEAWFZD21V)
    map[string]any{
    	"annotations": map[string]any{"incident.io/catalog-importer/last-sync-at": string("2024-06-26T22:46:36+01:00"), "incident.io/catalog-importer/sync-id": string("incident-io/catalog"), "incident.io/catalog-importer/version": string("2.2.3")},
  - 	"categories":  []any{},
  + 	"categories":  []any{string("team")},
    	"color":       string("cyan"),
    	"created_at":  string("2024-03-25T09:00:08.944Z"),
    	... // 12 identical entries
    }
```