Add a11y features to post editor context menu

Adding an .onTapGesture modifier here to dismiss the keyboard removes focus from whatever textview is active in the post editor, which prevents VoiceOver from getting confused about which accessibility frame should be read.

iOS/PostEditor/PostEditorView.swift

@@ -117,8 +117,19 @@ struct PostEditorView: View {
                         }
                     }
                 }, label: {
-                    Image(systemName: "ellipsis.circle")
+                    ZStack {
+                        Image("does.not.exist")
+                            .accessibilityHidden(true)
+                        Image(systemName: "ellipsis.circle")
+                            .imageScale(.large)
+                            .accessibilityHidden(true)
+                    }
                 })
+                    .accessibilityLabel(Text("Menu"))
+                    .accessibilityHint(Text("Opens a context menu to publish, share, or move the post"))
+                    .onTapGesture {
+                        hideKeyboard()
+                    }
                 }
             }
         }