Minor meta-improvements to the readme and packaging process

Merge remote-tracking branch 'origin/master'

Generates (hopefully) valid epubs now

Update nuget.yml

Added badges to readme

Restricted some class access and added in-memory file generation

Added some missing bits

Mimetype doesn't need to be editable

Donezo

Merge remote-tracking branch 'origin/master'

Mostly works

Idk templates or something

Init