Add linting the ensure new bundles include expected_result.txt and manifest.json

[cgraham-rs]

We need automated linting to protect from merges that include bundles that are missing required files to support Marketplace automation.

Otherwise when executing Connect Marketplace automation this can happen.

❯ pytest platform_integration_tests/tests/connect --tracing retain-on-failure --output test-results
========================================================================================= test session starts ==========================================================================================
platform darwin -- Python 3.11.7, pytest-8.2.2, pluggy-1.5.0
rootdir: /Users/christophergraham/dev/platform-integration-tests
configfile: pyproject.toml
plugins: playwright-0.5.0, dependency-0.6.0, base-url-2.1.0, retry-1.6.3, xdist-3.6.1
collected 0 items / 1 error                                                                                                                                                                            

================================================================================================ ERRORS ================================================================================================
______________________________________________________________ ERROR collecting platform_integration_tests/tests/connect/test_connect.py _______________________________________________________________
platform_integration_tests/tests/connect/content.py:68: in jump_start_bundles
    resp.raise_for_status()
.venv/lib/python3.11/site-packages/requests/models.py:1024: in raise_for_status
    raise HTTPError(http_error_msg, response=self)
E   requests.exceptions.HTTPError: 404 Client Error: Not Found for url: https://api.github.com/repos/rstudio/jumpstart_examples/contents/bundles/square-plot/expected_result.txt

During handling of the above exception, another exception occurred:
platform_integration_tests/tests/connect/test_connect.py:44: in <module>
    @pytest.mark.parametrize("bundle_name, expected_result", jump_start_bundles())
platform_integration_tests/tests/connect/content.py:70: in jump_start_bundles
    raise Exception(e)
E   Exception: 404 Client Error: Not Found for url: https://api.github.com/repos/rstudio/jumpstart_examples/contents/bundles/square-plot/expected_result.txt
======================================================================================= short test summary info ========================================================================================
ERROR platform_integration_tests/tests/connect/test_connect.py - Exception: 404 Client Error: Not Found for url: https://api.github.com/repos/rstudio/jumpstart_examples/contents/bundles/square-plot/expected_result.txt
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
=========================================================================================== 1 error in 3.17s ===========================================================================================