Remember last session for user

[cycomanic]

Great theme and it also works with the newer maintained https://github.com/JezerM/web-greeter/ without changes. I have a feature request. The theme does not remember the session based on the last logged in user. I'm sharing my PC with my family and we use different WMs. Currently we always have to remember to change the session when logging in. Could that be added?

I assume one has to add some callback that changes the session when changing the user. I had a look but didn't find an obvious spot where to add it (my js skills are very rudimentary).

[lepz0r]

JezerM/web-greeter#62