Consider still applying `need-triage` label to labelled issues created by external contributors

[simonbasle]

IIRC the bot still currently only applies the :question:need-triage label to newly created issues that don't have any label set.

This was originally done to work around issue creation in reactor-core, where for some reason the label(s) from the issue templates are not applied to the created issue when author is an external contributor.

The bot could probably check against a list of maintainers and still apply the need-triage label to newly created issues if the author is not a maintainer.