make header tabbable on assignment edit page
make header tabbable on assignment edit page

added role=heading and tabindex to "Published" to make tab-navigation
easier

fixes CNVS-7784

test plan
=========

- enable draft state
- navigate to the assignment edit page
- verify that the "Published" span can be tabbed to

Change-Id: I96836056606b45b07ab5c5e790a5245ac7f64390
Reviewed-on: https://gerrit.instructure.com/26191
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
QA-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>
Reviewed-by: Aaron Cannon <25919c673621c006b735dcd5a28df63325948e2b@instructure.com>
Product-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>

dgynn/canvas-lms,djbender/canvas-lms,utkarshx/canvas-lms,AndranikMarkosyan/lms,sfu/canvas-lms,wimemx/Canvas,SwinburneOnline/canvas-lms,leftplusrightllc/canvas-lms,landonwilkins/canvas-lms,gbleydon/canvas-lms,SwinburneOnline/canvas-lms,va7map/canvas-lms,utkarshx/canvas-lms,gbleydon/canvas-lms,arrivu/arrivu-lms,usmschuck/canvas,sdeleon28/canvas-lms,wrdsb/canvas-lms,Rvor/canvas-lms,greyhwndz/canvas-lms,wrdsb/canvas-lms,juoni/canvas-lms,whalejasmine/canvas-lms,va7map/canvas-lms,samuels410/greatlakes-lms,eCNAP/CANVAS,instructure/canvas-lms,loganrun/pincan,arrivu/hoodemo,antoniuslin/canvas-lms,kyroskoh/canvas-lms,roxolan/canvas-lms,sdeleon28/canvas-lms,snehakachroo1/LSI_replica,snehakachroo1/LSI_replica,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,whalejasmine/canvas-lms,whalejasmine/canvas-lms,arrivu/arrivu-lms,arrivu/qibla-ecampus,ShreniiNepal/shrenii_lmp,wrdsb/canvas-lms,venturehive/canvas-lms,dgynn/canvas-lms,skmezanul/canvas-lms,matematikk-mooc/canvas-lms,antoniuslin/canvas-lms,ShreniiNepal/shrenii_lmp,Jyaasa/canvas-lms,tgroshon/canvas-lms,arrivu/hoodemo,grahamb/canvas-lms,roxolan/canvas-lms,kyroskoh/canvas-lms,Unow/canvas-lms,eCNAP/CANVAS,samuels410/greatlakes-lms,SwinburneOnline/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,wye0220/shindig-canvas,juoni/canvas-lms,HotChalk/canvas-lms,juoni/canvas-lms,tgroshon/canvas-lms,samuels410/greatlakes-lms,kyroskoh/canvas-lms,HotChalk/canvas-lms,redconfetti/canvas-lms,whalejasmine/canvas-lms,shidao-fm/canvas-lms,antoniuslin/canvas-lms,va7map/canvas-lms,greyhwndz/canvas-lms,greyhwndz/canvas-lms,skmezanul/canvas-lms,snehakachroo1/LSI_replica,leftplusrightllc/canvas-lms,grahamb/canvas-lms,landonwilkins/canvas-lms,fronteerio/canvas-lms,loganrun/pincan,HotChalk/canvas-lms,dgynn/canvas-lms,efrj/canvas-lms,jay3126/canvas-lms,arrivu/qibla-ecampus,eCNAP/CANVAS,narigone/canvas,skmezanul/canvas-lms,arrivu/qibla-ecampus,Jyaasa/canvas-lms,samuels410/greatlakes-lms,Jyaasa/canvas-lms,usmschuck/canvas,dgynn/canvas-lms,greyhwndz/canvas-lms,utkarshx/canvas-lms,fronteerio/canvas-lms,jay3126/canvas-lms,redconfetti/canvas-lms,AndranikMarkosyan/lms,antoniuslin/canvas-lms,wye0220/shindig-canvas,venturehive/canvas-lms,sfu/canvas-lms,redconfetti/canvas-lms,Rvor/canvas-lms,shidao-fm/canvas-lms,djbender/canvas-lms,wimemx/Canvas,efrj/canvas-lms,efrj/canvas-lms,sfu/canvas-lms,HotChalk/canvas-lms,juoni/canvas-lms,narigone/canvas,instructure/canvas-lms,tgroshon/canvas-lms,arrivu/hoodemo,djbender/canvas-lms,jay3126/canvas-lms,landonwilkins/canvas-lms,ShreniiNepal/shrenii_lmp,Jyaasa/canvas-lms,shidao-fm/canvas-lms,loganrun/pincan,shidao-fm/canvas-lms,narigone/canvas,roxolan/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,jay3126/canvas-lms,sdeleon28/canvas-lms,wye0220/shindig-canvas,venturehive/canvas-lms,va7map/canvas-lms,kyroskoh/canvas-lms,wrdsb/canvas-lms,skmezanul/canvas-lms,arrivu/arrivu-lms,landonwilkins/canvas-lms,tgroshon/canvas-lms,instructure/canvas-lms,Rvor/canvas-lms,sfu/canvas-lms,snehakachroo1/LSI_replica,fronteerio/canvas-lms,gbleydon/canvas-lms,usmschuck/canvas,AndranikMarkosyan/lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,sdeleon28/canvas-lms,AndranikMarkosyan/lms,grahamb/canvas-lms,narigone/canvas,matematikk-mooc/canvas-lms,Unow/canvas-lms,redconfetti/canvas-lms,usmschuck/canvas,efrj/canvas-lms,Unow/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,Rvor/canvas-lms,venturehive/canvas-lms,eCNAP/CANVAS,SwinburneOnline/canvas-lms,ShreniiNepal/shrenii_lmp,grahamb/canvas-lms,utkarshx/canvas-lms,leftplusrightllc/canvas-lms,leftplusrightllc/canvas-lms,wimemx/Canvas