feat: allow searching articles in omnisearch (#11558)

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/views/api/v1/accounts/search/_article.json.jbuilder

@@ -0,0 +1,8 @@
+json.id article.id
+json.title article.title
+json.locale article.locale
+json.content article.content
+json.slug article.slug
+json.portal_slug article.portal.slug
+json.account_id article.account_id
+json.category_name article.category&.name