Hi Herby,
We were not yet considering implementing such support for Gogs/Gitea. You can of course create a feature request in our issue tracker: https://youtrack.jetbrains.com/issues/TW
We will considering implementing Gogs/Gitea support if more users vote for such an issue.
We are considering making pull requests more of a first class citizen in TeamCity though. There are no specific plans in respect to TeamCity version yet, and there was no feature request about it in our tracker, but I have made one now: https://youtrack.jetbrains.com/issue/TW-64392 When (and if) this is done it may become significantly easier to develop a third party plugin supporting Gogs/Gitea.