Add Jobs link to Defend

Why is this change being made?

We should advertise on our handbook page about our open jobs. This is a first iteration, in the future we can find a way to render the list of actual open jobs, but for now it's better than the placeholder we have.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what