fix: add examples below application/json in openapi schema file

[Kumzy]

Closes

#4558

Running the following file, examples are correctly setup regarding openapi documentation, they are visible using /schema endpoint.

from __future__ import annotations

from typing import Annotated, Any

import uvicorn

from litestar import Litestar, post
from litestar.openapi.config import OpenAPIConfig
from litestar.openapi.spec import Example
from litestar.params import Body


@post("/items")
async def create_item(
    data: Annotated[
        dict[str, Any],
        Body(
            examples=[
                Example(summary="Example A", value={"name": "Widget"}),
                Example(id="custom-id", summary="Example B", value={"name": "Gadget"}),
            ]
        ),
    ],
) -> dict[str, Any]:
    return data


app = Litestar(
    route_handlers=[create_item],
    openapi_config=OpenAPIConfig(title="Test API", version="1.0.0"),
)

if __name__ == "__main__":
    uvicorn.run("test:app", reload=True)

---

📚 Documentation preview 📚: https://litestar-org.github.io/litestar-docs-preview/4572

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.87%. Comparing base (9587ba1) to head (b64b772).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4572   +/-   ##
=======================================
  Coverage   97.87%   97.87%           
=======================================
  Files         292      292           
  Lines       15077    15081    +4     
  Branches     1703     1704    +1     
=======================================
+ Hits        14757    14761    +4     
  Misses        184      184           
  Partials      136      136           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[sobolevn]

This is a breaking change technically, if you disallow .update in users' typing. It is not a big deal, but I would keep this annotation unchaged if possible :)