fix reaction picker spacing and size

lib/src/reaction_picker.dart

@@ -78,7 +78,12 @@ class _ReactionPickerState extends State<ReactionPicker>
                             -1;
                         var index = reactionIcons.indexOf(reactionIcon);
 
-                        return RawMaterialButton(
+                        return ConstrainedBox(
+                          constraints: BoxConstraints.tightFor(
+                            height: 24,
+                            width: 24,
+                          ),
+                          child: RawMaterialButton(
                             elevation: 0,
                             padding: const EdgeInsets.all(0),
                             clipBehavior: Clip.none,
@@ -129,6 +134,7 @@ class _ReactionPickerState extends State<ReactionPicker>
                                 );
                               }
                             },
+                          ),
                         );
                       })
                       .insertBetween(SizedBox(