feat(misc): Add platform categories for backend code

[PixelDust22]

This mirrors the same file on the frontend and it allows us to check if a platform is mobile or not.

[github-actions]

🚨 Warning: This pull request contains Frontend and Backend changes!

It's discouraged to make changes to Sentry's Frontend and Backend in a single pull request. The Frontend and Backend are not atomically deployed. If the changes are interdependent of each other, they must be separated into two pull requests and be made forward or backwards compatible, such that the Backend or Frontend can be safely deployed independently.

Have questions? Please ask in the #discuss-dev-infra channel.

[scefali]

@Neo-Zhixing I'm concerned about copying the full contents of this file here as we don't really need it. I know you have a note to update this file, but people are going to inevitably forget it. Can we just use the mobile list for now?

[PixelDust22]

imo it's better to hard code the list than copying just the mobile section (there are a few places in the code base that are doing this btw).

A better approach might be creating a JSON file that the frontend and the backend both reads, however that'll be a lot more difficult to do. Calling for modifying both files is the right thing to do here imo.

Wonder what others would think about this.