Replace obs-websocket-api copy with CMake target

[tytan652]

Description

Replace obs-websocket-api copy with CMake target

Motivation and Context

Avoid maintaining copies of obs-websocket-api where we can use the target.

How Has This Been Tested?

Builds on my machine

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.