UX: Allow translation of composer icons

config/locales/client.en.yml

@@ -1065,8 +1065,10 @@ en:
       hide_preview: '« hide preview'
 
       quote_post_title: "Quote whole post"
+      bold_label: "B"
       bold_title: "Strong"
       bold_text: "strong text"
+      italic_label: "I"
       italic_title: "Emphasis"
       italic_text: "emphasized text"
       link_title: "Hyperlink"
@@ -1084,6 +1086,7 @@ en:
       olist_title: "Numbered List"
       ulist_title: "Bulleted List"
       list_item: "List item"
+      heading_label: "H"
       heading_title: "Heading"
       heading_text: "Heading"
       hr_title: "Horizontal Rule"