ci: run test workflow on PR edited (#113)

By default pull request triggers on event types `opened`, `reopened`,
`synchronize`.
See
https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request
Added also trigger on event type `edited`.

Resolves #87

.github/workflows/test.yaml

@@ -5,6 +5,7 @@ on:
     branches: [main]
   pull_request:
     branches: [main]
+    types: [opened, edited, reopened, synchronize]
   merge_group:
     branches: [main]