Add dependabot to check security and dependencies

[odysseu]

Hi
Wouldn't it be great to have dependabot check on this repo if they aren't any security alerts or dependencies to update ?
I suggest to enable it and have it scan this repo every week for a start (then probably every month or less often).

There needs to be 2 steps:

• enable dependabot in the project's settings (see screenshot)
• add a .yml file in the github workflows