Add and test swagger UI theme

[umar-anzar]

Issue Suggestion: Enhancing Swagger UI with Theme Customization

To improve the appearance of Swagger UI, consider exploring additional theme options for syntax highlighting. For example:

app = FastAPI(swagger_ui_parameters={"syntaxHighlight.theme": "obsidian"})

This changes the theme to "obsidian," providing a sleek, dark appearance.

Check out other available themes and experiment to find the best look for your UI. A well-chosen theme can make the UI more visually appealing and user-friendly.

For reference, see the FastAPI documentation: Change the Theme