Swap width and height in RGBImgObsWrapper, add test

[catanzaromj]

Description

This PR swaps the order of width and height for RGBImgObsWrapper, fixing a bug noted in #444. It also adds a test to verify the assertion statement from that issue.

Fixes #444

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Screenshots

Please attach before and after screenshots of the change if applicable.

N/A

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes