FIX: Adjust reviewable menu placement on mobile (#11420)

Shows the actions dropdown above the triggering button to avoid some
options from displaying below mobile navigation in DiscourseHub.

app/assets/javascripts/discourse/app/components/reviewable-bundled-action.js

@@ -1,11 +1,21 @@
 import { alias, gt } from "@ember/object/computed";
 import Component from "@ember/component";
+import discourseComputed from "discourse-common/utils/decorators";
+import { isRTL } from "discourse/lib/text-direction";
+
 export default Component.extend({
   tagName: "",
 
   multiple: gt("bundle.actions.length", 1),
   first: alias("bundle.actions.firstObject"),
 
+  @discourseComputed()
+  placement() {
+    const vertical = this.site.mobileView ? "top" : "bottom",
+      horizontal = isRTL() ? "end" : "start";
+    return `${vertical}-${horizontal}`;
+  },
+
   actions: {
     performById(id) {
       this.attrs.performAction(this.get("bundle.actions").findBy("id", id));

app/assets/javascripts/discourse/app/templates/components/reviewable-bundled-action.hbs

@@ -8,6 +8,7 @@
     options=(hash
       icon=bundle.icon
       disabled=reviewableUpdating
+      placement=placement
     )
   }}
 {{else}}