Bug 1884981 - Import history from another browser section on Firefox View History tab would not announce the context for buttons on it. r=fxview-reviewers,kcochrane

Adding a grouping markup on the `import-history-banner`, so the text outside of the focusable CTAs is being announced to a screen reader user.

Note: the heading remains implicit (being only styled to look as such but it is not marked up appropriately an is a generic `<span>`)

Differential Revision: https://phabricator.services.mozilla.com/D206272

browser/components/firefoxview/history.mjs

@@ -491,12 +491,19 @@ class HistoryInView extends ViewPage {
           class="import-history-banner"
           hideHeader="true"
           ?hidden=${!this.shouldShowImportBanner()}
+          role="group"
+          aria-labelledby="header"
+          aria-describedby="description"
         >
           <div slot="main">
             <div class="banner-text">
-              <span data-l10n-id="firefoxview-import-history-header"></span>
+              <span
+                data-l10n-id="firefoxview-import-history-header"
+                id="header"
+              ></span>
               <span
                 data-l10n-id="firefoxview-import-history-description"
+                id="description"
               ></span>
             </div>
             <div class="buttons">