Custom Firefox Mimetypes.RDF for Non-Profit

I'm seeking a skilled developer to create a customized mimetypes.RDF file for Firefox. This is for a U.S.-based non-profit organization. The main goal is to set up a specific association for a new custom file extension. We already have a customized mimetypes.rdf file for certain file extensions. We just need one more.

Key Requirements:
- Custom Application Associations: The mimetypes.RDF file needs to link certain custom file extensions with specific applications.
- File Types: The developer will be dealing primarily with custom file extensions, not standard ones.
- Application Handling: Firefox should be configured to open these custom file extensions with designated applications, rather than prompting to save or showing a download dialog.

Ideal Skills:
- Proficiency in creating and modifying Firefox's mimetypes.RDF file.
- Experience with custom file extension handling.
- Understanding of application association within browser environments.
- Ability to deliver a solution tailored to the needs of a non-profit organization.

The successful freelancer will help streamline our operations by ensuring Firefox correctly handles our unique file types.