[Nix Docs] Mention Nix and Android Studio in section about JDK

Summary:
Android Studio will require a JDK installation. Although JDK is
provided by nix develop, it is not accessible to Android Studio outside of
the nix development shell.

Include instructions to nix documentation on how to install the JDK using
sdkman to provide a JDK installation at a stable path.

https://linear.app/comm/issue/ENG-2170

Test Plan: N/A, mostly copied from existing documentation sources.

Reviewers: ashoat, varun

Reviewed By: ashoat

Subscribers: tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5655