Improvement: provide an .epub version of the book with releases

[pflavio]

Is your feature request related to a problem? Please describe.
No problem, just a suggestion.

Describe the solution you'd like
It would be great to have a .epub version in addition to the .pdf version to better read the book on ereaders. .pdf files don't reflowable nor resize well which makes them that much harder to read.

Describe alternatives you've considered
none

Additional context
vscode-pandoc could be used to do it in one click from the .md files (similar to creating the .pdf) in VSCodium.