LTI 1.3 instructor documentation for Canvas

[rhinopotamus]

Turns out that Canvas hides the "+App" button behind "View App Configurations", so it may be good to add that to the documentation.

Subsubsection: LTI 1.3 Instructor Setup - Canvas

[bnmnetp]

@ascholerChemeketa - wanted you to see this one.

[ascholerChemeketa]

Thanks @rhinopotamus. I will add that screenshot to the instructor guide.

[ascholerChemeketa]

RunestoneInteractive/InstructorGuide#26

[rhinopotamus]

Looks great!