Low hanging a11y fixes (#230)

This PR contains a few quick fixes for issues unearthed in the recent
accessibility audit.
Fixes FXVPN-429, 431, 434, 436, 427, 433, 437.

Author: lesleyjanenorton

src/components/message-screen.js

@@ -61,8 +61,12 @@ export class MessageScreen extends LitElement {
       <vpn-titlebar title=${this.titleHeader}></vpn-titlebar>
       <div class="inner">
         <div class="upper">
-          <img class="${this.identifier}" src="/assets/img/${this.img}" />
-          <h1>${this.heading}</h1>
+          <img
+            class="${this.identifier}"
+            src="/assets/img/${this.img}"
+            aria-hidden="true"
+          />
+          <h2>${this.heading}</h2>
           <slot></slot>
         </div>
         ${when(
@@ -225,7 +229,7 @@ export class MessageScreen extends LitElement {
       background: var(--action-button-color);
     }
 
-    h1 {
+    h2 {
       font-family: var(--font-family-bold);
       margin-block: 16px;
       color: #3d3d3d;
@@ -267,7 +271,7 @@ export class MessageScreen extends LitElement {
     }
 
     @media (prefers-color-scheme: dark) {
-      h1 {
+      h2 {
         color: #ffffff;
       }
 

src/ui/firstRun/firstRun.js

@@ -43,7 +43,7 @@ export class FirstRunPage extends LitElement {
       <main>
         <h1>${tr("thankYouForAdding")}</h1>
         <div class="flex-row">
-          <img src="firstrun.svg" />
+          <img src="firstrun.svg" aria-hidden="true" />
           <div class="copy">
             <p class="bold p1">${tr("optionalDataCollection")}</p>
             <p class="p1">${tr("first-install-body")}</p>