[Feature Request] Additional Resources for the e-Book and PDF Reader

[josh3way]

Is your feature request related to a problem? Please describe.
The reader (e-Book and PDF) is very minimal and comfortable, but there are some key features that are missing:

1. Highlighter
2. "Make available offline" for PDFs and e-Books.

These key features would greatly improve simultaneous reading of a PDF and writing in Cryptee documents.

Describe the solution you'd like
A highlighter would be an amazing addition to the reader. Sometimes, when you are reading a PDF and taking notes at the same time, marking up the text is a key feature. The speed for downloading and decrypting PDFs and e-Books is very slow; it would be fantastic if there were an option to save them offline, similar to what is already implemented for documents.

Additional context
For the highlighter, when you select text, a highlighter box could open with a few common colors, like this:

Additionally, it would also be interesting to have a list showing all the highlights made, along with a link to take you directly to them.

Best regards,
Josh. ❤️