srgb - adds submission type info

fixes CNVS-11236

test plan
=========
* in screenreader gradebook
* select an assignment
* verify that submission type is correct
* check multiple assignment types :)

Change-Id: I4fc24aecb048bf1518ae00c1ddd6149e12a38873
Reviewed-on: https://gerrit.instructure.com/30263
Reviewed-by: Cameron Sutter <csutter@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Liz Abinante <labinante@instructure.com>