fix: broken skip link in Learner Dashboard (#522)

Co-authored-by: Deborah Kaplan <deborahgu@users.noreply.github.com>

src/App.jsx

@@ -80,7 +80,7 @@ export const App = () => {
       <div>
         <AppWrapper>
           <LearnerDashboardHeader />
-          <main>
+          <main id="main">
             {hasNetworkFailure
               ? (
                 <Alert variant="danger">

src/__snapshots__/App.test.jsx.snap

@@ -17,7 +17,9 @@ exports[`App router component component initialize failure snapshot 1`] = `
   <div>
     <AppWrapper>
       <LearnerDashboardHeader />
-      <main>
+      <main
+        id="main"
+      >
         <Alert
           variant="danger"
         >
@@ -49,7 +51,9 @@ exports[`App router component component no network failure snapshot 1`] = `
   <div>
     <AppWrapper>
       <LearnerDashboardHeader />
-      <main>
+      <main
+        id="main"
+      >
         <Dashboard />
       </main>
     </AppWrapper>
@@ -75,7 +79,9 @@ exports[`App router component component no network failure with optimizely proje
   <div>
     <AppWrapper>
       <LearnerDashboardHeader />
-      <main>
+      <main
+        id="main"
+      >
         <Dashboard />
       </main>
     </AppWrapper>
@@ -101,7 +107,9 @@ exports[`App router component component no network failure with optimizely url s
   <div>
     <AppWrapper>
       <LearnerDashboardHeader />
-      <main>
+      <main
+        id="main"
+      >
         <Dashboard />
       </main>
     </AppWrapper>
@@ -127,7 +135,9 @@ exports[`App router component component refresh failure snapshot 1`] = `
   <div>
     <AppWrapper>
       <LearnerDashboardHeader />
-      <main>
+      <main
+        id="main"
+      >
         <Alert
           variant="danger"
         >