Update third_party_envs.md

[JorasOliveira]

Description

Adding DSSE: Drone Swarm Search env to the 3rd party envs list.

Type of change

• This change requires a documentation update

Screenshots.

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have run pytest -v and no errors are present.
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• 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

[JorasOliveira]

@jkterry1 @benblack769 could someone just give this a quick look please?