chore(release-notes): use main semantic tag

Author: EdricChan03

projects/rss-reader/src/app/pages/release-notes/release-notes.component.html

@@ -1,4 +1,4 @@
-<div class="app-content mat-typography">
+<main class="app-content mat-typography">
   <h1 id="app-header">Release notes</h1>
   <h2 id="current-version">Current version: {{ releaseNotes.latestVersion }}</h2>
 
@@ -39,7 +39,7 @@ <h3 id="version-{{ version }}" class="version-header">
     </ng-container>
   </ng-container>
 
-</div>
+</main>
 <ng-template #noReleaseNotes>
   <div class="center">
     <h2 id="no-release-notes-available">No release notes available!</h2>