chore: update actions/add-to-project digest to 0a99102

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This PR contains the following updates:

Package	Type	Update	Change
actions/add-to-project	action	digest	a800ee6 -> 0a99102

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[barmac]

Cross-posting my stance on this:

Generally, depending on a tag of an external repo is considered to be less secure. If an evil actor can make their commit into the repo with that tag, that means they can automatically hack our system.
However, the add-to-project action is part of the official GitHub actions org, and we already depend on tags of other repositories within this org, e.g. https://github.com/camunda/camunda-modeler/blob/develop/.github/workflows/CI.yml#L12. So depending on a tag of add-to-project would be a consequence of the trust we have already put into that org.
IMO it's OK how we do it, and I'd rather focus on minimazing the potential impact of the action being compromised. In that specific case, that would mean the GH token passed to the workflow should have only the permissions required to perform the specific action.