Add support for other Schoology instances

[nothingneko]

Describe the bug
Schoology Plus only works on schoology.com

To Reproduce
Go to a Schoology page other then schoology.com (eg schoology.spps.org)
No features

Additional context
Add support for more domains

[glen3b]

Hello! It looks like we're already tracking this at #82; if you could add anything additional in that ticket we'd appreciate it. I'm going to close this as a duplicate; if you believe this to be in error, please comment why.