LTI: Improve client experience and customizability

[ccgauche]

This issue is a collection of ideas to be discussed about what an user should be able to do and what it can customize.

• Have a panel on client side (Maybe the extension) that sets some cookies in the client
• Another option is to sync with the server but this is not really good for privacy since it enables fingerprinting
  Customization possible
• Container width
• Background color and foreground theme
• Font size and family
• Word spacing
• Download and upload stylesheets
• (Maybe use directly CSS through people can inject font request that break privacy)
• Change behavior on exiting the session link auto-redirection image inversion
  More privacy options:
• Fetch yourself images (Should we ask the server to or ignore the re encoded ones)
• Disable images
• Disable code (Syntax highlighting)
• Create a protocol to send the RAW data unformatted as HTML (Could be useful for an android app or desktop app)