Resolve "Add Wider Community Marketing KPI chart to handbook"

Why is this change being made?

The data team is embedding the Wider Community KPI to the dashboard and we are updating the KPI page to have an icon.

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

Closes #6505 (closed)