Add PDF as a file type that can be handled

[joeprivettsmart]

Please could you add PDF as a type of file that can be handled by the build process and extracted to the __assets folder?

https://github.com/remix-run/remix/blob/main/packages/remix-dev/modules.ts

[machour]

👍🏼

Would you like to open a pull request to the dev branch adding support for it?
Here's an example with the zip file extension: #3985