Refactor MIME type and file extension mappings into separate modules

[chigwell]

As a developer, I would like to refactor the MIME type and file extension mappings in the detect_language() function of lang.py to separate modules, to improve code organization and maintainability.

Background

The current implementation of the detect_language() function in lang.py has mappings for MIME types and file extensions defined within the same file.

Proposed Changes

1. Create mime_mappings.py module containing the mime_to_language dictionary.
2. Create extension_mappings.py module containing the extension_to_language dictionary.
3. Update detect_language() function to import mappings from the new modules.

Acceptance Criteria

• A new module mime_mappings.py is created containing the mime_to_language dictionary.
• A new module extension_mappings.py is created containing the extension_to_language dictionary.
• The detect_language() function is updated to import mappings from the new modules.
• The mime_to_language and extension_to_language dictionaries in the new modules are kept in sync with the original mappings in lang.py.
• The lang.py file is updated to remove the original mappings for MIME types and file extensions.
• The changes do not introduce any new bugs or issues in the detect_language() function.

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