Update to web-greeter ^3.0.0

[JezerM]

web-greeter ^3.0.0

A lots of these kind of themes are outdated, depending of an abandoned project: lightdm-webkit2-greeter, later renamed to web-greeter, made by Antergos team. However, Antergos left some updates and a little direction to what this project should evolve.

web-greeter 3.0.0 is now my fork, where I'm trying to develop this project, with some other new features.

You can check my fork here (web-greeter 3.1.1), and the API docs here.

Aether theme

As I said previously, these kind of themes are outdated. However, they look pretty nice! Therefore, it would be a shame to not use them, and for that reason I'm trying to fix some big issues about these themes, such as deprecated functions or concepts.

That being said, merging this PR will mean that this theme won't be usable with lightdm-webkit2-greeter at all, but it will allow to have features like battery status, brightness controller, layout selector, and a newer JavaScript engine with Chromium.

Changes

• Removed deprecated functions and concepts
  • lightdm.start_session_sync to lightdm.start_session
  • user.real_name to user.display_name
  • user.name to user.username
  • Global functions like authentication_complete or show_prompt are needed to be attached to its correspondant signals, like lightdm.authentication_complete.connect(() => authentication_complete())
  • theme_utils.dirlist needs a callback function due to qt5webengine limitations.
• Upgraded to webpack 5
  • The behavior is practically the same
  • Removed some unnecessary dependencies