feat: add geojson support on media of a form

[sijandh35]

Checklist

1. Make sure that your code lints and that you've followed our coding style
2. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
3. Mention any related issues in this repository (as Support For Geojson On Media Upload of a Form #5014) and in other repositories (as kobotoolbox/other#ISSUE)

Description

Added support for .geojson MIME type to allow uploading geojson files in media files when using the select_one_from_file {filename}.geojson field type in KoboToolbox forms. This resolves the validation issue that prevented the geojson file from being uploaded.

Notes

The KPI backend validation was updated to include the .geojson MIME type, which allows users to upload geojson files as media files in the Kobo form builder. This enhancement ensures that forms using the select_one_from_file {filename}.geojson field type can now properly utilize geojson files.

Related issues

Fixes #5014