Update travel page to include a link to the sponsored travel section.

Why is this change being made?

The change is being made as there exists some differences between normal travel and sponsored travel when it comes to expenses. Since the already exists a sponsored travel page in the handbook, we should add a section to the travel page of the handbook linking to the sponsored travel section.

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