Setup dependabot

[tomaspalma]

We should have dependabot which a handy utility in order to automatically update packages.

This is also important because it allows us to be more updated with package security updates and it creates pull requests automatically that we can then merge, instead of manually checking for every package or having to manually know which packages have had a security vulnerability update.

One good example of that is in a PR in the nijobs repository NIAEFEUP/nijobs-fe#295