[COMPONENT] Page Header

[mraysu]

We want a shared component for the page header. All pages will have the same header, so it would be convenient if they all shared the same styling.

Figma. The header would consist of the image element with the text header and subheader overlay. All pages will render their contents below the header.

Next.js Documentation for applying root header.

For your PR

Create a header component that allows a custom image url, header, and subheader fields.
For testing, show a few example pages with different headers.