forgejo support

@mih has deployed https://codeberg.org/matrss/forgejo-aneksajo on https://hub.datalad.org/ and I expect us to get even more CI actions being done on such deployments. Samples of action runs could be

- https://hub.datalad.org/forgejo/datalad-clone-action/actions

Here is some docs on API: https://forgejo.org/docs/latest/user/api-usage/ which point to then https://hub.datalad.org/api/swagger and seems have quite a rich API on `/actions/` e.g.

```
❯ curl --silent -X 'GET' 'https://hub.datalad.org/api/v1/repos/forgejo/datalad-clone-action/actions/tasks?limit=4' -H 'accept: application/json' | jq . | head -n 20
{
"workflow_runs": [
{
"id": 254,
"name": "clone-get-deep-content",
"head_branch": "main",
"head_sha": "eee0779214a28f769d89907c11fb608d60dfad73",
"run_number": 62,
"event": "push",
"display_title": "Add more usage examples",
"status": "success",
"workflow_id": "test-action-live.yml",
"url": "https://hub.datalad.org/forgejo/datalad-clone-action/actions/runs/62",
"created_at": "2024-08-30T10:50:56Z",
"updated_at": "2024-08-30T10:51:29Z",
"run_started_at": "2024-08-30T10:50:56Z"
},
{
"id": 253,
"name": "clone-recursive-no-data",
```

although I have not yet found on where/how to fetch artifacts (logs) upon a quick look... might be that is under different component/API since iirc it is a different component which actually provides CI jobs execution. May be @mih knows.

Start with the existing GitHub Actions, Travis, and Appveyor support in the repository, then review the Forgejo API documentation and the /actions/ endpoint shown in the issue. Determine how Forgejo exposes workflow logs and artifacts, and define completion as downloading the relevant action run logs and artifacts from Forgejo deployments.

Written by the indexing model from the issue text.