feat: docx-pdf conversion (#40)
* feat(document): add a way to convert pdf to docx using libreoffice
* feat(documents): add the ability to convert docx to pdf using libreoffice
* test(document): test both new features
* ci(github-actions): install libreoffice on github actions
* refactor(files): add a new method to the file interface to support mime types as they can differ from the know extensions
* refactor(documents): add a new constant to the document package for docx
* refactor(files): add the new method to every struct that implements the file interface
* build(docker): install libreoffice at the release stage
* docs(readme): add a new table on what's new in terms of file conversion
* build(dockerfile): replace debian bookworm with debian trixie just to have more up to date image
* refactor(pdf): add two buffers as stdout and stderr to see what's goin on at the time to convert pdf to docx
* fix(pdf): use %q to make the filename a double-quoted string safely escaped with Go syntax
* refactor(pdf): print the stderr when it is not empty
* refactor(docx): replicate the changes added to the pdf file
