improve course tile navigation option tags for SRs

Fixes: CNVS-33256

Test Plan:
Open the dashboard tab
Using a screen reader tab to the course card icons for course discussions, etc.
Verify screenreader has appended the course name to the icon description

Change-Id: Ida59f4f8472ed81936dd2e42a310385887e20a88
Reviewed-on: https://gerrit.instructure.com/101750
Tested-by: Jenkins
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Dan Sasaki
Product-Review: Simon Williams <simon@instructure.com>

app/jsx/dashboard_card/DashboardCard.jsx

@@ -175,13 +175,14 @@ define([
     linksForCard: function(){
       return this.props.links.map((link) => {
         if (!link.hidden) {
+          const screenReaderLabel = `${link.screenreader} - ${this.state.nicknameInfo.nickname}`;
           return (
             <DashboardCardAction
               unreadCount       = {this.unreadCount(link.icon, this.state.stream)}
               iconClass         = {link.icon}
               linkClass         = {link.css_class}
               path              = {link.path}
-              screenReaderLabel = {link.screenreader}
+              screenReaderLabel = {screenReaderLabel}
               key               = {link.path}
             />
           );