Add Economic Benefits Box

[jjstnlee]

first sprint!!!
For this sprint, we are adding new information for a project called Economic Benefits.

1. Update the Project type in /types/schema.d.ts to include a new attribute called economic_benefits that will be of type string or null.
2. We are using styled components so create a new styled div called EconomicBenefits in styles.ts then use this in index.tsx.
3. We want it to display only if economic_benefits is not an empty string/is not null. To see how to do this you can refer to the lines of code below.
4. If you want to test the styling, for now you can just include random text and ignore the 3rd step, but once the styling looks good, make sure it doesn't appear when economic_benefits is null.
5. You can probably reuse the DetailsContainer from styles.ts like how it is being used below.