+Add support for multiple sections

[diiigle]

Fix for #21

Started with Projects and will port the same mechanism to the other sections as well. But feel free to give some feedback already, especially on the typescript best practices (got virtually 0 experience there)!

Summary

It queries for File nodes instead of specific *Json nodes now, and filters inside the component. Not ideal (the filtering could happen in graphql already), but that its the only way possible with staticQueries (and without variables).

Updated the documentation to the best of my knowledge. The example content could be a lot more creative.

Progress

• [x] About
• [x] Contact
• [x] Hero
• [x] Interests
• [ ] ~~Legal~~ already contains a filtering mechanism
• [x] Projects