Add securitySchemes example for multi-file structure

[jessica-schalz]

Describe the problem to be solved
No current example exists for a multi-file directory structure using multiple different forms of authentication.

Describe the solution you'd like
Include a components/schemas/securitySchemes example to illustrate how to implement the structure in other projects.

Describe alternatives you've considered
Also nice to add: examples in the multi-file guide.

Additional context
N/A