* extract extension based on file's content
* Add python-magic dependency
* fix the _estimate_extension function and lowercase the file extensions
* check if the FileTypeClassifier can be imported
* add test and new file types
* fix typing
* import Optional
* revert Optional and make sure a string is always returned
* fix test so that it skips markdown files
* Emulate Code & Docs action
* Generate schemas
* Tidy up test code & extensioness files
* Improve error messages
* Revert schema changes
* Emulate black and docs CI again
