[lib] Reorder types in media-types.js

Summary:
No logic changes. While types can be used before declaration, validators are just standard objects and can only be used after declaration. Moved a few types down so that we can add the validators next to them (in the future diff).
Depends on D7564

Test Plan: Run app on web and ios, check if they throw any unexpected errors.

Reviewers: kamil, inka, tomek

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7565