Convert PowerPoint and Word files under `docs/cna` to PDFs

[Marcono1234]

Currently https://github.com/CVEProject/cveproject.github.io/tree/master/docs/cna and its subdirectories contains multiple PowerPoint (*.pptx) and Word (*.docx) files.

This is neither very accessible, since it requires you to download these files to view them, and you need some kind of office program to view them. Additionally, from a security perspective using PowerPoint and Word files is quite bad, given that they are widely used to distribute malware through macros or by exploiting bugs in office programs.

Could you please consider converting those files to PDFs (in case that is possible without losing information)? That would allow directly viewing them in the browser.