add readable label to the home link in breadcrumbs
add readable label to the home link in breadcrumbs

fixes CNVS-6704

test plan:
  * navigate to a course home page;
  * using a screen reader, navigate to the breadcrumbs and
    verify that the home breadcrumb is read as, "My
    Dashboard."

Change-Id: I099b41597b16ff8136d216b6d1e2d86fc61918b8
Reviewed-on: https://gerrit.instructure.com/24209
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Braden Anderson <a6cc2cef7d25f27847876bdb81651755fcebacf0@instructure.com>
QA-Review: Cam Theriault <b4133c36b6d893d0872cc09e87b536d16aa2d241@instructure.com>
Product-Review: Zach Pendleton <514dbb4d54d4f29e454990df7d075678f43f92aa@instructure.com>

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