add component explaining the definition + value of oral history

[lisjak]

• about modal doesn't have any verbiage explaining oral history and why we have focused on narrative collection
• will make the mission statement of the eviction stories map more prominent and more accessible to laypersons
• this will also provide us with an opportunity to be very transparent about our narrative collection and publication process as related to the COVID maps
• may entice more narrators to come forward and share story through education re: the value of oral history
• design TBA