brain FNO example

[yjihyuny]

Modulus Pull Request

Description

Brain example 1st PR

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.
• [x] The CHANGELOG.md is up to date with these changes.

Dependencies

[NickGeneva]

Closing since merged in PR: https://github.com/NVIDIA/modulus/pull/242