Fix issue/comment menus

Closes https://codeberg.org/forgejo/forgejo/issues/1120

- Adds labels to reaction and context menu.
- Fixes taborder in markdown combobox buttons. They are now only one
  "tab" stop and can be navigated with arrow buttons and in the right
order (previously, it would skip the table button).
- Generates more verbose output for the reactio selectors to provide
  content for users who cannot identify the meaning of these buttons
visually. Explicit aria-labels are now preferred over auto-generated
ones.

web_src/js/modules/tippy.js

@@ -103,7 +103,10 @@ function switchTitleToTooltip(target) {
       }
     }
     target.setAttribute('data-tooltip-content', title);
-    target.setAttribute('aria-label', title);
+    // only replace if not explicitly set
+    if (target.getAttribute('aria-label') !== null) {
+      target.setAttribute('aria-label', title);
+    }
     // keep the attribute, in case there are some other "[title]" selectors
     // and to prevent infinite loop with <relative-time> which will re-add
     // title if it is absent