Enable Dependabot on this repository

[thierry-martinez]

I would like Dependabot to be enabled on this repository to keep requirements‑dev.txt up‑to‑date, as it is in the main Graphix repo. Note that I am not an admin on this repository, so I cannot enable it myself.

[shinich1]

@thierry-martinez I just made you an admin of this repo.

[thierry-martinez]

Thank you, @shinich1!