fix vertical button margin in dialogs

src/explorer/replaceImportDialog/replaceImportDialog.scss

@@ -6,5 +6,9 @@
 .#{bp.$ns}-dialog.pb-explorer-replaceImportDialog {
     .#{bp.$ns}-dialog-footer-actions {
         flex-direction: column;
+
+        .#{bp.$ns}-button {
+            margin: 0;
+        }
     }
 }

src/sponsor/SponsorDialog.tsx

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2022 The Pybricks Authors
+// Copyright (c) 2022-2023 The Pybricks Authors
 
+import './sponsorsDialog.scss';
 import { AnchorButton, Classes, Dialog, Intent } from '@blueprintjs/core';
 import classNames from 'classnames';
 import React from 'react';
@@ -24,6 +25,7 @@ const SponsorDialog: React.VoidFunctionComponent = () => {
 
     return (
         <Dialog
+            className="pb-sponsors-dialog"
             title={i18n.translate('title', { pybricks: 'Pybricks' })}
             isOpen={showDialog}
             onClose={() => dispatch(sponsorHideDialog())}

src/sponsor/sponsorsDialog.scss

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2023 The Pybricks Authors
+
+@use '@blueprintjs/core/lib/scss/variables' as bp;
+
+.#{bp.$ns}-dialog.pb-sponsors-dialog {
+    .#{bp.$ns}-dialog-footer-actions {
+        flex-direction: column;
+
+        .#{bp.$ns}-button {
+            margin: 0;
+        }
+    }
+}