Load officer images using GraphQL data layer

Due to time constraints in deploying the fall 2020 redesign, officer images had to be placed in the `assets` directory to be loaded into the website. However, because of the nature of this data, it should use Gridsome's built-in [GraphQL data layer](https://gridsome.org/docs/fetching-data/#images) as opposed to having indirect references to photos in the site assets.