Merge rights for Fabian Kosmale

Fabian is one of the approvers working on qtdeclarative full-time, together with Ulf. As there's quite a bit of work happening in 5.14, 5.15 and soon dev, merge conflicts appear regularly in the QtQml related modules that he's working on. He's therefore qualified to help resolve the conflicts.

I have asked him about whether he's comfortable using git merges and whether he has done them in the past (outside of Qt). He responded positively and he understands our branching model and the role of the merge bot.

Therefore I think him having merge rights would improve the merge conflict resolution process for qtdeclarative.